Got the following affiliate email from 'em:
We'llgive each of your customers who registers at Mercata for the first time a $100 store credit, good for up to 20 percent off future purchases (excluding taxes and shipping). But like the last offering, be sure to act on this special quickly: It will expire on June 15, 2000 (and all store credit earned through the offer must be used by June 30, 2000).
FYI for anyone who hasn't registered with 'em.. now's the time. I think Apex has a link to click through to them.