Lots of people (myself included) had been saying that Facebook was overvalued pre-IPO. I don't say this as any testament to any investment acumen I purport to possess (on the contrary, I largely suck at particularly short term share trading). What I do mean is that as an outsider with some cursory research and common sense, this was entirely predictable.
The only unknown with the IPO was how irrational the market would be and I'm glad to see it wasn't.
The people who say "look at the eyeballs they have; the sky is the limit" are the last people you should take investment advice from. Facebook had (and has) two primary sources of revenue: advertising and virtual goods. Valued against similar companies it was overvalued. And still is (IMHO).
I think this piece overstates that Facebook was attempting to hide things here. It's natural that any IPO will try to disclose as little as possible and try to be as positive as possible while stil being truthful and accurate.
Personally I may think of buying in if its gets down to $10-12.
Even so, Facebook is an extremely risky investment. Instagram is a cautionary tale here: from nothing to existential threat that you need to buy-to-shelve for $1 billion in two years... well, I guess it doesn't take much to threaten Facebook.