A little bit worried about the US Treasury Bill

We have seen how US investment fund rushed into US property market, rushed into stock market and commodity market. All the three have burst. Now we are seeing a rush of fund into US Treasury bills. The short term 4-week bill has dropped from 3.08% in January 2008 to 1.95% in June, 1.63% in September and on 4/12/08 it touched 0.01%. 13-week bills have dropped in a similar way from 3.26% in January to last week low of 0.02%. The belief is "US Government will not default." To push the rate down to o.o1% indicates a mad rush into Treasury Bills, the safest asset. It appears to me that this is another bubble. What will happen if due to some reason, a panic stampede to get out of treasury bills takes place ??? September 2008 record shows that at the top three places, China is holding US$585 billion, Japan is holding US$573 billion and UK is holding US$338 billion with the rest of the world holding US$1.702 trillion giving a total of US$2.86 trillion. The top three is holding 52% of the total treasury bills issued until September 2008. I can't think of any reason why these three counties should unload their holding indiscriminately. No danger in the near future.