Why Warren Buffett wouldn't invest in Apple or Google

The Oracle of Omaha has a second rule: Don't buy companies you don't understand

Buffett with University of Nebraska cheerleaders Saturday. Photo: Lane Hickenbottom/Reuters

FORTUNE -- Some 18,300 people -- more than attended Barack Obama's massive campaign kickoff Saturday -- showed up for Berkshire Hathaway's (BRK-A) annual shareholder's meeting in Omaha yesterday. And judging from the New York Times' live blog, it was a lot of fun. There were cartoons and comedic skits and celebrity appearances, including Bono, Bill Gates and Debbie ("Buffett Rule") Bosanek, his now-famous secretary.

But what made the headlines Sunday were Warren Buffett's remarks about Apple (AAPL) and Google (GOOG):

• "I would not be at all surprised to see them be worth a lot more money 10 years from now but I would not buy either one of them."
• "I sure as hell wouldn't short them either."
• "We couldn't predict what would happen to Apple 10 years ago and we can't predict what will happen to it 10 years from now."
• "The chances of being way wrong in IBM (IBM) are probably less, at least for us, than the chances of being way wrong in Google or Apple."
•  "I just don't know how to value them."

That last remark, as Reuters points out, echoes Item No. 5 (out of 6) in Berkshire Hathaway's Criteria for Acquisition:

(5) Simple businesses (if there's lots of technology, we won't understand it)

Good rule.