Shares of Motorola Mobility (NYSE: MMI) spiked as much as 23% yesterday. The reason for the surge, however, wasn't immediately apparent … until suddenly, it was.

Irrational exuberance, thy name is Icahn
Carl Icahn, the mogul who's been agitating for change at Motorola for years, had another bright idea yesterday. Inspired by the frenzied bidding among Apple (Nasdaq: AAPL), Research In Motion (Nasdaq: RIMM), and Microsoft (Nasdaq: MSFT) over Nortel's collection of telecom patents earlier this month, and by Google's (Nasdaq: GOOG) interest in buying IP powerhouse InterDigital (Nasdaq: IDCC) yesterday, Icahn yesterday made a very public proposal to Motorola.

In a filing with the SEC, Icahn urged the company to sell its patent portfolio to a well-heeled bidder. Some pundits say Motorola's portfolio of patents is at least as valuable as the one Nortel just sold off, and if that's the case, a sale could immediately monetize as much as $4.5 billion of Motorola's past research.

A crazy idea?
Icahn's proposal does make you wonder how Motorola would continue manufacturing cell phones after selling off the intellectual-property rights to manufacture cell phones. But there are ways around that. A sale of its patent portfolio to Apple, for example, with simultaneous licensing of said patents back to Motorola, would enable Motorola to stay in business. Motorola would, in essence, be receiving a hamburger today and gladly paying for it on Tuesday. There's a method to such madness.

Alternatively, Motorola might dump off its patents to cash-rich Google, which is notorious for collecting technology and then giving it away to Android licensees to profit off Internet advertising that makes use of the tech. That way, Motorola might monetize its patents immediately and perhaps avoid having to pay for their use at all.

Foolish takeaway
In short, the price spike at Motorola, although unexpected, isn't quite as crazy as it looks. And as I've said before, even at 156 times earnings but just 14 times free cash flow, Motorola isn't nearly as expensive as it appears.

Will Motorola take Icahn up on his crazy plan? Add the stock to your Fool Watchlist, and find out.

Fool contributor Rich Smith holds no position in any company mentioned. Check out his holdings and a short bio. The Motley Fool owns shares of Google, Microsoft, and Apple. Motley Fool newsletter services have recommended buying shares of Google, InterDigital, Microsoft, and Apple and creating a bull call spread position in Apple. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.