I read about it, it's a very big undertaking and I highly doubt they're even going to make a dent into Facebook. Some of Anonymous doesn't even agree with or want to go through with this operation. My estimate is (and this is pretty generous, IMO) 460,000 anons actually going through with this. That being said, Facebook can easily take this extra load of traffic. Facebook has 60,000 servers and serves 600,000 pictures a second (from 2009).
60,000 servers and 460,000 anons. With load balancing, that's roughly 7 people attacking per server. With Facebook's server hardware and customized HTTP/MySQL servers, this is a very poor attack.
tl;dr, Facebook isn't going anywhere anytime soon.
EDIT: Not 30,000 servers, now it's 60,000.
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