FB is simply going to utilize a different vector which as other posts have suggested may or may not be better than search history, among the other piece of data utilized by Google.
FB has data that Google has been eagerly attempting to garner (with little success) and exploit to enhance targeted advertising. In this environment, one is not only able to take advantage of the direct personal information revealed by the user but also able to infer additional information by analyzing the users social network and it's complex relationship web. This is extremely powerful.
In fact, a particular advantage of utilizing such a vector proposed by FB is that it does not rely on search history. Just because I'm searching for "Albert Einstein" does not mean I'm interested in a book on relativity or a search for Bob Dylan I'm suddenly going to buy his CDs. In stead, analyzing my social network will allow for the ability to display ads generated by my social network which in theory are relevant irrespective of my search history profile. Example, FB can easily deduce that a close friend of mine with whom I frequently attend "clubs" (by analzying event history) has purchased a clubbing shirt. An ad of this type may be more relevant than a Bob Dylan CD.
This could even go further and this interference could occur in a completely different social circle that happens to correlate with my social network.
Extremely powerful tool.