I am shocked at the market cap loss YHOO is experiencing right now due to this story.. I've seen breaking news drive stock price fluctuations but this is pretty extreme.
What's keeping it up is the continued possibility of a stockholder revolt, which is precisely what needs to happen. (Supposedly, someone was organizing it, but I haven't followed along.) The stockholders need to oust the whole board, and replace it will a cleanup crew, who'll sell out to microsoft.
A google/yahoo buyout won't happen. The gov't (hopefully) wouldn't allow it.