Kind of interested in this -- I get rid of a good bit of extra crap using freecycle and craigslist, and when I'm inundated with responses, I sift through them with a quasi-first-come-first-served approach. In other words, the email saying "I take it" may be the first one I receive, but the person who is a few emails later but is genuinely interested in all of the stuff and can communicate in complete sentences ends up being the one to whom I reply.
I always thought this was at my discretion as the giver/seller. Is there a code to this whole thing? I viewed it as a risk of buying used -- no guarantees. I may adjust if this is a major faux pas.