Bloomberg details:

An extension of the U.S. Build America Bond program was left out of a compromise that President Barack Obama struck with congressional leaders to prolong tax cuts enacted in 2001 and 2003, White House officials said.

This wasn't all that unexpected...

Concern that the program would lapse has weighed on the tax-exempt bond market since an end to Build America issuance may boost the amount of money state and local governments borrow with tax-exempt debt. Issuers have also rushed to sell Build America securities before year-end.

And with yields at more attractive levels and supply set to collapse, the opportunity to buy is "apparently" now. CNBC details:

Just weeks before the Build America Bonds program is set to expire, issuance and demand for the government-subsidized notes have reached a fever pitch.

Pricing pressure from a glut in supply, uncertainty over changes in the government’s subsidy levels, and a spike in the Treasury’s 30-Year bond—to which municipal notes are typically pegged—have pushed yields higher, according to investors.

Some investors and analysts say this may be the sweet spot for buying the Build America Bonds, which are now the fastest-growing part of the $3 trillion municipal debt market. “We think we’re at the high for yields,” says one muni bond investor. “If you’re going to buy, now is the time.”

Source: Barclays Capital