Here is the real financial assessment:
From the low-to-the current rally high (477-550) Google appreciated some 14.8%.
Quite a move. But looking past the obvious, the market (in this case the Nasdaq which better represents Google) had a +10% appreciation in the same time frame.
Google saw a market differential of approximately 4-5%. So 15% of that $20B was purely due to the overall market movement, which leaves 5% (or $1B) to company specific data.
Basically, the market maybe placing a $1B due to Google+. And despite the nice move on GOOG, the market is currently pricing Google's businesses with an ex-cash multiple of 16.5. Considering its growth, and prospects, not pricey by any stretch of the imagination.
TechCrunch, stick to what you do best, providing information and access to insight like the video embedded below, not financial fluff.