After briefly becoming the third-largest company in the US - as measured by market capitalization - Apple (AAPL) is now quietly returning the slot to Walmart (WMT).  Last week, Apple experienced a surge in valuation as its iPad went public (for pre-order).  A concomitant drop in Walmart shares prompted the position change. 

As of the final bell on Friday, Apple commands a market cap of just over $201.5 billion, compared to a Walmart cap of more than $210.5 billion.  And so the rankings revert to their original positions. 

Microsoft (MSFT) and Exxon (XOM) remain far ahead, and Berkshire Hathaway (BRK-A) lags with a valuation of roughly $202 billion, also as of Friday close.