Melting Permafrost: Methane Release

From Alaska, where trees are tilting and housing is collapsing from warming temperatures, to the Arctic, where vast amounts of methane are being released from melting permafrost, comes a disaster looming on the horizon:
http://www.latimes.com/news/science/environment/la-na-global-warming22-2009feb22,0,646220.story
The description of the positive feedback mechanism is especially troubling...

Thanks Rod

The deep-sea clathrates have been mentioned for awhile as possible future positive feedback mechanisms.

Given an economical way to harvest the clathrates, we could burn them as fuel, thereby reducing the forcing effect to <= 5 percent of the methane? Assuming the article's statement, "Methane (CH4) has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide (CO2)."

A greener tundra would provide a new carbon sink, which would affect the equation to some degree?