Mish writes on the treasury bubble and why it might not burst soon. I agree with him - just because something gets beyond what we thought two months ago was reasonable doesn't mean it has to fall today. It can just exist for a long time.
Besides, shorting using TBT would be a bad idea - because of the structure of these ultrashort ETFs. They do double the daily returns - not annual returns. All these ultrashort ETFs are good only for day-trading, not for investing. I want to find a way of shorting treasuries where I am happy to hold the position for 5 years.