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What is Yahoo really worth? That's the $44.6 billion question, the one that ultimately split Steve Ballmer and Jerry Yang. Most pundits predicted Yahoo's shares would drop precipitously today, perhaps as low as $19, where they were trading before Microsoft's offer. Instead, they're trading around $24.60 — a 14 percent drop, but a 30 percent premium to the pre-Microsoft price. The shares could drop further over the course of the day, but it's worth asking what's sustaining Yahoo's shares at this level right now.

It could be stock-market arbitrageurs who believe that Ballmer's walk-away was just a negotiating tactic. (Silicon Alley Insider finds this scenario unlikely.) Or it could be optimism about prospective profits from a deal to outsource Yahoo's search advertising to Google, though that deal has yet to be announced, let alone proven to work.

But there simply may not be enough people selling to take Yahoo's shares lowers. The buy-and-hold investors who were holding out for a price in the high 30s would be hypocritical to sell now. If the mutual funds who own so much of Yahoo really think Yahoo was worth that much, oughtn't they be buying? (Chart by Yahoo Finance)