Over the past two years, the shares of mobile-phone companies have rallied sharply, both in absolute terms and relative to the S&P 500 index.
Since September 2005, the Dow Jones U.S. Telecommunications Sector -- which has an equivalent exchange-traded fund, the iShares Dow Jones U.S. Telecommunications Sector Index Fund (NYSE: IYZ) -- has gained 40%, outpacing the broad market by more than 21 percentage points.
Despite all the euphoria, a number of recent developments suggest the bullish tide is turning and the sector could be in for a rough ride in the weeks and months ahead.
Consider the following:
Growing competition. Last Friday, BloggingStocks' Douglas McIntyre noted that "an all out price war" brewing in Japan could be a sign of things to come in a saturated U.S. market.
Tesla Roadster sets a record -- travels 313 miles on a single charge
Cramer on BloggingStocks: China's industrial focus helps lots of U.S. names 
Why do we have a weak dollar?
