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Microsoft is trying to buy Yahoo because it believes online advertising will be a much bigger business than it is today, and it wants to have a piece of the pie. Yahoo has a massive number of users, and the second-largest share of Internet searches. But usage, by itself, just means you have to open up pricey datacenters and hire expensive engineers. What matters is revenues. And on that score, Google utterly rules the lucrative search-advertising market.

This chart from search-engine marketer Efficient Frontier shows, outside the U.S., Yahoo is a financial nonentity. Japan, the exception, does not count: Yahoo Japan is separately traded, and not part of Microsoft's offer. $44.6 billion for a company which will not substantively improve Microsoft's market share in search advertising. This is an Excel bug I have yet to hear about.