When rates are low, the only thing that can happen may be ... bad
The Way We Live Now - No Safety in Numbers - Are Treasury Bonds a Bubble That May Someday Burst? - NYTimes.com:
"Warren Buffett wrote: “When the financial history of this decade is written, it will surely speak of the Internet bubble of the late 1990s and the housing bubble of the early 2000s. But the U.S. Treasury bond bubble of late 2008 may be regarded as almost equally extraordinary.”"
Rates could go up ... and therefore bonds would go down.