Ok first of all, its those people in suits up at jupiter media (or is it internet.com)'s marketing dept that deside on the ads.
And secondly, this is a free service that they are supplying to us. We don't pay to be able to use it, and they have to get the money from somewhere to pay for bandwidth, upgrades, heck, they even have to pay for vBulletin (ok, so its not v expensive, but it's still a cost).
This is a really good free board and if keeping it that way involves having adverts, then so be it. As I said in a different post, it may be a little bit annoying, but I'd much rather have it than pop-ups (which are No. 1 in Piers' all-time internet pet hates (tm) 😉), and after a while, you'll just learn to ignore them.