Oligopoly (corrected, where's the spell check Standard!?!) exists so no acquisition necessary at this time. More likely is MSN to buy ASK or AOL or another second or third tier search engine.

I believe this tender is a move by MSN to draw Google out of the weeds since there is talk of a partnership between the two.

My question is who are the four firm's in the search Oligopoly or is there one at work at all here?
Oligopoly
From Wikipedia, the free encyclopedia
Oligopoly is a common market form. As a quantitative description of oligopoly, the four-firm concentration ratio is often utilized. This measure expresses the market share of the four largest firms in an industry as a percentage. Using this measure, an oligopoly is defined as a market in which the four-firm concentration ratio is above 40%.