Count me as one of the folks that believes Google ought to fix search before it takes on the juggernauts of the consumer web. But that could just be the SEO in me talking.
If your friends "like" a Stack Exchange post but not Experts Exchange, isn't it obvious how this would help them filter out the bad ones?
If the answer is no, then any algorithm that takes into account collective searches and 'likes' will ignore them because they wouldn't fit within the cluster of people relevant to that search term.