Since most boards are populated by spam, political garbage and posts that can leave Yahoo open to litigation it is not unthinkable. Adding to that that most users have ad blockers resulting in very little revenue going to Yahoo and the high cost of policing and maintaining the message boards it would not come as a big surprise.
The problem is, for every ad-blocker Gloom uses to make sure Yahoo doesn't make a dime off him, Coldone has an "ad-hopper" program that jumps to every ad on Yahoo, and clicks on it incessantly. His PC looks like one of Christmas light displays synced to Gagnam Style, but he is very proud to have calculated he added at least 5 bucks to the bottom line of YHOO Last quarter, approximately .0000000000000001 per share. Of course, he also burned out 3 PC's in the process.