Mr. Ballmer in the hotseat

At Microsoft's annual shareholder meeting this week, CEO Steve Ballmer stated the company is "done with all acquisition discussions with Yahoo."

He added, however, that Microsoft remains "very open" to an online search collaboration.

Ballmer's statements sent Yahoo shares plummeting 20% — too soon after the stock's 10% leap following CEO Jerry Yang's resignation.

Microsoft made an unsolicited $47.5 billion bid for Yahoo in February. The latter rejected it in three different instances, opting instead to initiate a sponsored search liaison with larger rival Google. That deal fell through earlier this month when federal regulators threatened to levy an antitrust lawsuit against the search firms.

Yahoo's stock closed Wednesday evening at $9.14 — one-third of its value at the time Microsoft proposed the buyout.