You're right, yaminb, Facebook does pit the concept of the "wisdom of crowds" against the "wisdom of friends". There was an interesting segment on 20/20 this week about the very topic. They pointed to an interesting example. On "Who wants to be a millionaire?", polling the audience (the crowd) results in a correct answer more than 90% of the time, whereas the call to their friend resulted in a correct answer only 2/3 of the time.
Having said that, I think it's cliche to take an extreme position, either positive or negative, when talking about Facebook. Yes, it's useful. Yes, it's overrated.