Facebook was over-valued, simply put. When the stocks launched it was placed higher than some of the very large oil companies, and you have to think that Facebook doesn't actually give anybody anything, it's just a service and it makes its money mainly through advertisements, whereas oil companies are producing goods for the general consumption. Just because Facebook has millions of users, which a lot of are fake/double/dormant accounts, then no wonder the stock value fell.
But Internet websites like Facebook go in and out of 'trend' quite quickly- look at Yahoo and even MySpace. Sure, MySpace never reached the heights of Facebook but that doesn't mean that some other social media site will come along and steal some of Facebook's share.
In my opinion, I don't think Facebook will be all that popular in a few years time. It can't keep growing and growing because there's only so many people that can have a Facebook account and people will eventually get bored of reading the same old status updates ("got work in the morning, BOOO" or "like for a rate", grrrr). But who knows, it's a market that no one really fully understands.
