Many advertisers expected the CPC (cost per click) prices to go up after the Yahoo / Microsoft adCenter transition was complete.
One advertiser said in a WebmasterWorld thread he CPC prices "soared" by 40%. He said:
We are seeing a 40% increase in click costs on average since late September on existing AdCenter campaigns. Our transitioned campaigns are seeing a similar percentage increase when compared to what we were paying with Yahoo.
The costs are so out of control, he has pulled and pause his campaigns with adCenter. He said:
We have paused all of our campaigns within AdCenter as they no longer yield a positive ROI... and we're not talking about a tinker-toy budget either - deep 7 figure annual ad-spend.
Have you seen the same? Please take our poll and ask your friends to take it as well:
Forum discussion at WebmasterWorld.
Update: There is a good white paper on this at SearchFuel.

Comments:
Michael Martinez
10/19/2010 07:11 pm
Yet another nail in the coffin of the myth that the Yahoo!-Microsoft merger would bring more choice to consumers.
Aaron
10/20/2010 08:50 pm
We don't have to worry about pulling ads -- our impression levels have nearly disappeared, even after a substantial increase in bid.