Microsoft could also decide to make an offer directly to shareholders, called a tender offer, which would put more pressure on Yahoo's board to negotiate. At the same time, Microsoft could also set a deadline for its bid, known as an “exploding offer”.
And if Microsoft decides to make this a nasty battle, it could start a proxy contest to oust Yahoo's board at its next election; it would have until March 13 to nominate a new slate of directors.