In the opening chunk of his Annals, the Roman historian Tacitus claims he will write his history of early Roman empire sine era et studio – without anger or favouritism. It is, of course, a huge whopper. Tacitus can't bear to tell a story without bias creeping on to the page: he is the man who describes Nero's improvement to Rome's building regulations after the Great Fire of Rome with the phrase, "In parts of Rome unfilled by Nero's new palace…"

This, obviously, doesn't make Tacitus a less valuable source of fact and opinion. It just means that historians have to read him – and every other source they ever use – with care. Tacitus's experiences under the imperial system coloured his views of his subject matter, because he was a person first, and a writer second.

I think this is worth bearing in mind as high-minded people rush to judge Wikipedia and find it wanting. Particularly in the light of Philip Roth's recent letter to The New Yorker. Roth found an error in the Wiki entry on The Human Stain, and wrote in to ask that it be corrected. He was told by an administrator that he – the author – was an insufficiently credible source. A secondary source would be required before a change could be made.

This clearly reveals a flaw in their system: two or more bad sources are not as good as one authoritative source. The world is full of half-truths and lies – finding two of them in agreement is not the same as finding a fact. Morgan Freeman, Eddie Murphy and Jackie Chan have all been killed several times over this year online, but are all still (at the time of writing) not dead. Fifty people reporting a corpse they've read about isn't the same calibre of evidence as one pathologist filing his report.

And Wikipedia has its weaknesses: on contentious issues, it struggles to contain bias, and it's subject to vandalism (in which people maliciously edit pages to reflect their personal views). But it is still a great resource on many subjects, and its best pages are packed with links to the sources from which they are drawn. Even if you don't trust Wiki, you can still use it as a signpost to other information.

The Roth story illustrates this perfectly: he wrote a lengthy open letter, which was published around the world, because he is Philip Roth, and when he writes a shirty letter, people pay attention. A less-known figure might well struggle to emend a Wiki entry, because the papers wouldn't print their words. And indeed, newspapers aren't always truth tellers themselves.

But the entry on The Human Stain has now been edited to include some of Roth's letter. So the public record of what we know about this book has been improved. And perhaps in future, Wiki administrators might allow that the quality of a source is more important than quantity.

Beware Hermione

An internet security survey has revealed that she is the most popular bait for cyber crooks trying to lure you into downloading malware. Search for Emma Watson, and you have a one in eight chance of hitting a malicious site in your results. She's replaced Heidi Klum, last year's internet Mata Hari.

Unsurprisingly, almost every one of the riskiest celebs to search for is female, because those searching for them are likely to click on links (often promising nude shots), and that's how the scam works.

So, the question is, who's looking for naked pics of Jimmy Kimmel (the only man in this year's top 20) or Piers Morgan (in last year's top 10)? Bleah.