Is Facebook Really Worth $15 Billion?

Apparently Microsoft believes that it is. I'm not sure whether this is a testament to the power of the social networking site or whether this is just the beginnings of another internet bubble. Facebook exploded so fast that I wonder whether it may end up being just a fad. Yes, it's exciting to encounter all these people you haven't seen in ages, it makes the first couple months of a Facebook membership fun. Inevitably though, the rate of finding friends wanes once you get closer to adding everyone you've ever known. This is not to say that it isn't still without its appeal, I just wonder what we'll think about Facebook in a couple years.