Well, the Yahoo! Microsoft deal is back in the news. I'm sure it makes some sense to the MBAs but in the technology arena, it makes none. Why?
In the technology arena there is an old saying that "You have to eat your own dog food." What does this mean? It means that you have to use your own technology products. If you're IBM, your business needs to run on IBM hardware and software. If you're Dell, there had better be al Dell on every desktop and every slot in the server room. If you're SAP, your business had better run off of SAP software. Why? It goes to the heart of credibility. If you don't use your own products, why should your customers want to? It's real tough to sell a product that you don't use, because it's clear that you don't really believe in it.
Back to Yahoo! and Microsoft. Microsoft makes the Windows operating system and .Net programming language. Yahoo is built on BSD operating system and PHP programming language. If Microsoft does buy Yahoo, they have two choices: continue to run mission-critical infrastructure on non-Microsoft software and lose credibility in the industry, or convert the Yahoo infrastructure to Windows. To 'eat their own dog food' they'll have to convert Yahoo to a Windows stack. This will take a monumental amount of effort/dollars/months. It will be a couple of years before the infrastructure settles down again. By that time the Yahoo/Microsoft online presence will be irrevelant.