Chances are you would be horrified. You always knew he was coming, but Big Brother would finally have arrived. Paranoia would not be the word; only sinister would apply.
Yet you would also be horrified to learn that the source of the information was not some shadowy underworld organisation, not the electronic tendrils of unchecked computer activity, not the product of a dark and covert network of informants. The source of most, if not all, the information is likely to have been you. And that information was probably freely volunteered.
The news yesterday that the National Blood Transfusion Service was considering a sponsorship deal that would see its list of 1.8 million donors opened up for the use of the makers of Hob Nob biscuits was greeted with outrage. Understandably, the thought of the service being sponsored at all caused upset.But there was also concern that the unfortunate 1.8 million would subsequently be bombarded by unwanted junk mail; that their names and addresses might even be sold and re-sold to a beast hungry for personal information.
However premature news of such a deal was - and the service was denying any such pact with the devil had been sealed - the mailing list aspect was unlikely to have been true. Under the Data Protection Act, such information would have to have been "fairly obtained" by the transfusion service, and donors would have to have been warned about any future use. Any deal that involved selling off names for a mailing list would probably, therefore, be blocked by Elizabeth France, the Data Protection Registrar, as the donors would not have expected their personal details to be exploited on a mailing list.
But is it such a bad thing to be on a mailing list in the first place? Since the 1970s, when direct - or junk - mailing first began to get on our nerves, its use has mushroomed. Today, more than two billion items of unsolicited mail are sent to households each year. A further 715 million are sent between businesses.
Direct mailing is a pounds 1bn industry, with more than 500 organisations gathering information or processing it, trying to send you mail that you will not describe as junk. No titbit is too small. Every scrap of information helps to draw a picture of you that the marketing men and women can use. As a result, information itself has become a commodity. It is mined, sold, rented and ruthlessly exploited.
Every organisation with customers or clients has information to sell. For a pounds 75 fee, they can register their intention to gather that information with the Data Protection Registrar and then, subject to it having been obtained and processed fairly, they can pass it on.
One newspaper report noted two years ago that Grand Metropolitan, the leisure group, was registered to hold information on its employees' relationships and sex lives, membership of voluntary bodies, their leisure interests and racial origin. And, it added, it wanted to hold the same information about rival staff.
Such goodies are eminently marketable. Simple lists of names and addresses can fetch pounds 85 per 1,000 names, and can be rented by list owners to users via list brokers, middle men who give companies the names most suited to their intended mailshot.
The amount of information already in storage is staggering. One of the biggest purveyors of marketing - not financial - profiles is Computerised Marketing Technologies Ltd of Teddington, south-west London. If you want to target mail at balding 30-year-old single men who drive a Golf GTi, wear Hush Puppies and breed labradors, CMT and companies like it can get you a list of thousands.
Sinister? Not really. The companies get such information simply by asking people about themselves. CMT sends out more than 50 million questionnaires each year, and more than half of us are daft enough or interested enough to fill them in and return them. The questionnaires, given titles like "The National Shopping Survey" or "The National Motoring Survey", encourage participation by offering shopping vouchers through the post a month later, or the prospect of a pounds 1,000 prize draw. People who fill them in are told that the information will be passed on to others.
Surveys ask about shopping habits, size, banking preferences, the time since a certain purchase was made (to discover whether it is about time someone persuaded you to buy again), and basic income, demographic and biographical details. Motoring surveys ask which car you drive, which petrol stations you prefer. They could even find out which radio station you listen to while you drive.
As a result, clients of CMT, such as Nestle, First Direct and Pedigree Petfoods, can find out who uses their products, or who would, if they received a free voucher through the post, which they undoubtedly will. Follow-up surveys are allowed to ask more personal questions, usually medically related.
Already, a picture has been built up that speaks volumes to the experts - who will now be able to walk up to you in the street and tell you how much you earn, what car you drive, details about your dog, and - oh dear - that you have a haemorrhoid problem.
Is all this really so terrifying? Evidence suggests that the public doesn't think so. Despite a 224 per cent increase in the amount of direct mail sent to people's homes in the past 10 years, the number of complaints about it fall each year. In 1989, the Data Protection Registry was receiving a thousand complaints a year about direct marketing - almost 45 per cent of all its complaints. Last year, it had only 300 complaints, 10 per cent of all gripes.
The Advertising Standards Authority also reports fewer upheld complaints about the use of personal information in mailshots, a paltry 24 in 1994, compared with 48 in 1993.
The direct mail industry argues that this is because the terrifying amount of information they hold in numerous databanks helps them to target more precisely, to give us more of what we want. To turn junk mail into welcome mail, to get that haemorrhoid cream where it is needed most.
If, however, you are still sceptical - and many of us are - you can write to the Mailing Preference Service, a body set up by the Direct Marketing Association to ensure that unwilling recipients of junk mail can be removed from records. More than 400,000 households have already taken up the option.
Or you can box clever. All of the sources of information used by the direct marketing industry must give you the choice of not having it passed on to third parties. Either they warn you that the information will be passed on if you buy a product - in which case, don't buy it - or they contain an opt-out box, which you can tick. If you think entry into a competition offering two weeks in the Bahamas is worth handing over some private information for, then go ahead. If not, buy a Lottery ticket.
There is nothing sophisticated about keeping your private business private. This may be the computer age, but old-fashioned methods - such as not revealing information - are still surprisingly effective. And if all else fails ... throw that junk mail in the bin.
How to keep your name off their lists
The Mailing Preference Service is an industry body that keeps - guess what? - a list of those who don't want to be on lists. Mailing companies consult it to purge their own lists - but purely voluntarily. And not all companies participate in the scheme. The Mailing Preference Service is on 0171-738 1625. Under the 1984 Data Protection Act, a company cannot pass on a customer's name without notifying the individual concerned. If you suspect a company has done this, the Data Protection Registrar may take action by issuing an enforcement order against the offending firm. The Data Protection Registrar is on 01625 535777. The Advertising Standards Authority is another avenue for complaint. It recommends that mail order firms give customers the choice of whether to have their details passed on. The ASA also recommends that mail order firms inform people, on request, exactly who knows what about them. These recommendations have no force in law, however. The ASA is on 0171-580 5555.Reuse content