“We are done with all acquisition discussions with Yahoo.” Stever Ballmer’s pronouncement yesterday landed like a ton of bricks, especially on Yahoo’s stock price, which fell almost 20 percent on the declaration. With Yang stepping down, the speculation was Microsoft might come back to the negotiating table. But if Ballmer is to be believed, this dance is over. Microsoft still needs to be more competitive in search to try and stop the Google juggernaut, and Ballmer is still very interested in some working relationship with Yahoo for search functions. But Ballmer has made it clear that buying all of Yahoo is now out of the question. It still isn’t over, but things look pretty bleak in Sunnyvale.