the one i've heard that i like the best is:
it's like PayPal, but it's free.
so trades are reversible? and support staff will help with disputes, but make you wait 2 weeks for a reply? and you can't pay for naughty things like wikileaks donations?
sounds awesome!
well, i know all that. but the thread title asked for a 'selling pitch'.
in case you've never done it (sell), you gotta get your foot in the door...
EDIT: ok, ok:
it's better than PayPal, and it's free.