Even though Yahoo's board may try to reject the Microsoft takeover, there is no resisting the borg. Microsoft will buy Yahoo.
If you haven't tried Microsoft adCenter, they have a great promotion for US customers: they give $50 in free clicks when you sign up for a Microsoft adCenter Account.
I've griped about usability in the past, but for many of my campaigns, AdCenter has the highest conversion rates, more than Google AdWords or Yahoo Panama. The problem is low volume.
In all likelihood, Microsoft will buy Yahoo, and AdCenter will eventually have 35%+ search market share.
So get ahead of the game, and get started learning adCenter today.