Inflation expectations, as seen in the yield differential between the treasuries and the inflation protected index. As the treasuries have gone way down since the QE II excitement. There is no other way to play the expectation of some inflation but to go negative on the TIPS. See if the 5 year is close to 0 and the TIPS are positive you will be saying that there will be no inflation at all in the next 5 years. So if 5 goes to 0 and you think that there will be at least 2% inflation you have to go negative on the TIPS.
Reading between the lines .... it says LIQUIDITY TRAP... now they have to take the TIPS out dancing and get TIPSY. http://wallstreetpit.com/49239-at-a-tipping-point