I don't believe that facebook is the technological fad that tech pundits want them to be. They have infected the infrastructure of the web in ways that livejournal and myspace never could.
I agree, but I would add that they're overhyped as well. I think Facebook's value is somewhere in the middle between current expectations / valuations and a fad. So yes it's big, it will continue to be big, but it's not and never will be Google big.
I could be completely wrong though considering the engineers who've left google for facebook, but then again, maybe that was just for a massive payout?