From the Wall Street Journal:
The effective interest rates on TIPS have collapsed to record lows. It is mathematically impossible now for investors to earn respectable returns from any of them, and in many cases they are a lock to lose money in real, inflation-adjusted terms.
At least you don't have to worry about losing money with Series I Savings Bonds, but of course I bonds have annual purchase limits. I have more info in my last I bond post
. It sure would have been nice if the Treasury didn't slash the limits in 2008.