Betting against Treasury bonds was supposed to be the no-brainer strategy for 2010. Instead, shorting government debt has brought steep losses so far this year, due to surging bond prices as investors seek safety on worries stocks could be hit by deflationary headwinds. The largest exchange-traded fund tracking the long end of the Treasury curve, the $3.3 billion iShares Barclays 20+ Year Treasury Bond Fund, has rallied more than 10% year to date. The ETF rose Friday in the wake of a disappointing July employment report.