Warren Buffett has gotten greedy too quickly while everyone else takes too long to become fearful, suggests the Wall Street Journal in today's "Heard on the Street" column.

Under the headline Even the Oracle Didn't Time It Perfectly, Peter Eavis writes that while Buffett has won "plaudits for some canny deals," there's also an "unnerving pattern emerging."

"Mr. Buffett looks to be committing his capital too early. On some bets, waiting might have gotten him better terms or more attractive entry prices."

"Time for the Oracle to get a new crystal ball," according to Eavis.

He acknowledges that Buffett doesn't try to time his investments too closely, and says he's not launching a "cheap gibe" based on the S&P's 7 percent decline since Buffett's 'I'm Buying U.S. Stocks' op-ed piece in the New York Times on October 17.

Instead, Eavis focuses on two bets Berkshire Hathaway has placed on derivatives.

In one, Berkshire received large payments to provide default protection for "certain junk-rated corporations" in North America. The company has already booked hundreds of millions of dollars in mark-to-market losses on its exposure to these credit default swaps. "Berkshire more than doubled it notional exposure on these CDS to $8.8 billion between the end of 2006 and the middle of this year."