By Robert Holmes

Warren Buffett recently said stocks will outperform gold and bonds, calling them the safest asset by far. He's putting Berkshire Hathaway's (BRK.B) money where his mouth is, buying up shares of DirecTV (DTV) and IBM (IBM).

In a Fortune article published last week, Buffett offered investors a preview of his upcoming annual shareholder letter. Buffett said equities will "prove to be the runaway winner," with the Oracle of Omaha talking down investments in gold and bonds. Regarding the latter, Buffett said bonds are a dangerous asset because they are currency-based and exposed to interest-rate risk.

During the fourth quarter, Buffett put some cash to work and bought several stocks. The billionaire opened a new...