I do. I require a 25% deposit and we work out the date at the same time. Anything not picked up by the negotiated date goes back in the shop and my policies say that they lose their refund. I've only had one person default, though, and I just returned her deposit (mostly because she did not follow through on anything and I didn't want to do any business with her -- at all).
I did this with 2 listings -- one for 25% of the purchase price, and then day of pick up, another for the other 75%. I'm not sure if there is a better way to do this, but it does work for me.