Similar to this, I noticed a pretty crappy thing Google are doing on Youtube on the ipad last night. I did a youtube search and went to tap the first result only to have it replaced with an ad just before I clicked it, taking me through to some ad.
I experimented with this a couple of times, both times I did a search, and about 0.5-1 second after the page loaded the first search result was shifted down and its position taken by an ad link that looked the same as a search result.
Similar annoying thing with video pre-roll ads on Youtube: I'm used to pausing videos by clicking on them but when the video is an ad then it opens the link of the ad instead of pausing the video.
I experimented with this a couple of times, both times I did a search, and about 0.5-1 second after the page loaded the first search result was shifted down and its position taken by an ad link that looked the same as a search result.