The tax on google---a semi thumbs-up

The Mail has this interesting story about a tax proposal hatched somewhere between Andy Burnham's DMCS and Mandelson's BERR to tax internet advertising to fund the BBC. I don't like the idea of shovelling more money at the BBC---I think there are lots of others providing public service content who need support (like us! Donate Here!)---but I like the idea of an online advertising tax. Taxes are basically a good thing when you put a cost on something that needs some degree of discouragement. This is why a carbon tax would be good. Advertising---and especially online advertising---falls into that category. Every time an advertisment mis-sells a product, it should be counted as a pure social cost. Moreover, in a world of internet search, I do not believe that someone who is actively searching for a product actually needs advertising---searching does the job if you know what you're looking for. And if you end up buying when you don't know what you're looking for, I think that the likelihood of a mis-sell---of buying something which does not corespond to your considered desire---is very high. That suggests that online advertising, which has a high private pay-off to the advertiser, also has a high externality, or social cost. So, Mandelson: yes, go ahead and tax online advertising; but Burnham, please sort out a way to support non-BBC public service providers.