NASCAR & tree planting

Interesting blog post at Cocktail Party Physics titled i think that i shall never see / a carbon offset as lovely as a tree.  It was inspired by a claim that "NASCAR offsets 100% of the carbon emissions from this race via their tree-planting program."  It's an example of bad (nonexistent, really) science.  It's relatively easy to show that their claim is ridiculous since they'd have to plant over 2,000 trees for each race (which they obviously aren't doing).  It's a good example of how you can hear a claim that sounds sketchy, do a little bit of analysis, and see if the claim is valid or not.  In other words, how to think!