There's a good read over at WorldWatch: "U.S. Under Pressure to Protect Tropical Forests".
The short of it:
To meet emissions reduction goals via cap & trade, polluters in more industrialized nations need to purchase carbon offsets.
Reducing rates of deforestation in less developed nations (allowing standing forests to stand) can offset carbon emissions cheaply and effectively.
Now, think about discount rates and incentives ... does this sound like "win-win"?
Note the discussion of risks. Ideas for how to mitigate those possibilities?