Seb Bishop: My business week

The star of Channel 4's Millionaires' Mission looks at the future of the free-for-ads model

Free mobile phone plan anyone? Yes, if you're aged between 16 and 24. And all thanks to Blyk, the new mobile phone that has been creating waves in the press this week. It offers free texts and calls in exchange for users accepting ads on their handsets. The "free" ad-supported model has just shifted into 5th gear.

Ad-supported services are not a new concept (think commercial terrestrial TV), but the last few years have delivered the second wave of the "free with ads" revolution.And we've also seen a literal Free-for-all in the newspaper market. We now have free directory enquiries services (0800 118 3733), free music downloads (SpiralFrog), free online TV (Joost), free men's mags (Monkey), and free phone calls (Skype). On the internet we can share compromising videos of friends on holiday; become world famous musicians without setting foot in a recording studio; And it's all for free, financed in the main through advertising.

The Blyk service now takes the model one step further and on to our most personal device – the one thing most of us carry 24/7/365. The mobile.

So what's the next logical step? Free flights with constant in-flight ads? Or driving into London's congestion charge zone free, provided we listen to ad supported "Radio TFL". But how far can, this model go? The answer hinges on that most fundamental of advertising principles – advertisers' return on investment.

I suppose my worry is this: how many businesses can the ad industry support? Surely there will come a point where the ad dollars are stretched too far and the costs outweigh the returns?

Advertising channels that are relevant to the services they're supporting, and generate good ROI for advertisers are likely to continue to grow. It's the channels where targeting and relevance are more tenuous that may struggle to stay on the media schedules.

Now, where did I put that free paper...?