AlyssaS - 7:15 pm on Feb 6, 2011 (gmt 0)
I'm saying the quality and nature of the alternative online ad market would change very quickly if Google used Adsense as a negative organic signal in some way.
Only if the advertisers complained. It doesn't matter if the publisher is upset by being downgraded in the SERPS, the success of an ad network and the migration of advertisers from one network to another, depends on advertisers.
I'm not sure Google advertisers would be upset if some of the bad content farms were zapped. Look at it from their point of view - they are paying good money for a lead, it's a big part of their budget - but may be getting clicks simply because the ad layout is such that clicking by accident happens a lot, or a lot of people clicking are looking for info, rather than clicking to buy i.e. the page didn't do a great job of filtering. That was the whole reason G cleaned out some of the worst Adsense publishers - it was because they were upsetting the advertisers. Zapping the worst content farms may increase the return on advertising for the advertiser.
If the advertisers remain happy with G and Adwords/Adsense, then even though publishers might sign up with other networks, it won't do them the slightest good if those networks don't pull in the advertisers too. They'll be served up with irrelevant ads (from lack of advertisers) and won't make a bean.
G has the ability to upset publishers and webmasters at will as long as their advertisers stay loyal and the searching public stays loyal.