Google (NASDAQ:GOOG). It's a noun. It's a verb.

It's a search engine. A social-networking toolmaker. A financial data provider. A mobile phone "maker." All of which makes it a rival to Time Warner's (NYSE:TWX) AOL, a partner with News Corp. (NYSE:NWS), an alternative to Yahoo! (NASDAQ:YHOO) Finance, and a software vendor to Motorola (NYSE:MOT).

In short, Google is fast becoming all things to all people. And today we learned that Google will also invest "hundreds of millions" of shareholder dollars in search of "Renewable Energy Cheaper Than Coal." Do these people not know the meaning of "diworsification"?

Google, listen carefully: I love that you're trying to change the world. It's great that you've adopted "Don't be evil" as your motto. But there's a reason why slower-growing energy companies like ExxonMobil (NYSE:XOM) and ConocoPhillips (NYSE:COP) command P/Es of around 12, while investors are willing to pay 52 times earnings for shares of the faster-growing and innovative Google.

Unlike selling clickthroughs, energy can be a risky business for Google, one that consumes enormous amounts of capital before ever generating a return.

So forget about "evil," Google. Stick to what you're great at, and don't be dumb.

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Fool contributor Rich Smith does not own shares of any company named above. The Motley Fool's disclosure policy is a floor cleaner and a dessert topping.