Yes, true. But, I think, social networking websites was born just due to lacking of social interaction (among real relationships) on web while people was spending more and more time on it for searching valuable information. Facebook just brings social information in real life on web and make social interaction much easier (although I think it only keeps us further away from real life).
In my point of view, Google is king in valuable information (just like knowledge or things you're interested in, that you always want more and more) and Facebook is king in social information (what you're not always interested in but you usually feel sorry when missing it). It's hard to say what kind of information is more important just like it;s hard to say wether Google or Facebook is worth more than the other.