From Webmasterresources.info :

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The Microsoft corporation announced earlier today that it is in the process of making an offer to buy Yahoo for about $45 billion dollars. The buy-out is an attempt for Microsoft to join forces with Yahoo to compete against Google in the Web search market.

Currently, Google controls about 79 percent of the worldwide Web search market while Yahoo is second with about 16 percent and Microsoft is a distant third with 4 percent.

If Microsoft is successful in buying Yahoo, it would be interesting to see how this affects Google’s current market dominance and if either Microsoft and/or Yahoo will drastically change their search algorithms. If so, this could result in changes in search engine optimization techniques used by webmasters.

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Do you think if Microsoft does buy Yahoo, it will change the Yahoo search algorithm?

I dont think they will make any major changes at first. I think they might once they decide on their strategy to take down Google.

I think Microsoft and Yahoo may have issues with a clash of cultures internally before even thinking about joining up to take on Google.

Yeah, makes you wonder if they can even work together

Yes there was a strong rumor making waves that Microsoft or Google will be purchasing Yahoo sooner or later.The bid will start at $44.7 billion dollars.Any inputs to this will be highly appreciated so that we would re-think about our optimization strategies.
As of now yahoo has rejected the MSN take over

I try to optimize using basic SEO principles, and not for any single search engine. That way I dont put all my eggs in one basket in case an algorithm change occurs.