I can't speak for college football recruits but I do know that when my son was being recruited for soccer, we checked out the forums of the three main schools that he was looking at. His cousin who was recruited by Big Ten schools for basketball did the same thing.
Its a good way to get a "feel" of the school, what the fans think about the team, coach, keep up on the latest news, who else has joined the committ list etc. Absolutely you read them with a grain of salt, but seeing specific players getting trashed on one forum made an impression and along with a couple of other things, got that school checked off the list.
These are 16 and 17 year old kids that are attached to their computers. Of course they read the forums. You can bet their parents read them too. After a loss, it is obvious there will be criticism but its when it crosses the line that it can make an impact on recruits AND their parents. Who wants to send their kid into a lion's den? You can bet there are some MOTHERS reading these boards. Its not just locker room or bar stool talk anymore.
I am on an Alabama board also. THAT forum was insane last night after they lost. Attacking the quarterback in thread after thread, threatening posts toward LSU fans, fire the offensive coach etc. Ridiculous because they almost beat the #3 team in the nation and THAT is not what you want your recruits reading.
Quite frankly, I would be surprised if recruits and their parents DIDN'T read the forums of the schools especially if they have given a verbal. When its your kid and that big of a decision, you look for any information outlet you can find. Imagining your kid in front of tens of thousands of rabid fans versus in front of fans that show respect is part of the decision making process. No one expects kid gloves and if you are playing in the big time you have to take the criticism. Its when its constant or unsubtantiated or just ugly that it can hurt the program.