If you can create arbitrage situations for customers you can generate a decent amount of buzz in certain circles. Off the top of my head one way to do it is to offer to buy gift cards for more than 95% of their value. Some people have credit cards that give them back 5% on grocery store purchases and many grocery stores sell gift cards. If the folks on FatWallet Finance (http://www.fatwallet.com/forums/finance) get wind of it (heck, post it yourself) they'll jump all over it and you've got immediate exposure to hundreds of people. I would set limits though and do it only sporadically lest you end up w/ a huge surplus of gift cards that may take you a while to sell.

To get a sense for the kind of exposure you can get here's a thread from another arbitrage situation (buy dollar coins from the US government at face value, collect credit card rewards/cash back, deposit coins into bank account). These guys went nuts and the US Mint policies were actually changed to combat it. There's an article somewhere from a press conference where the US Mint publicly addressed it but I'm too lazy to dig it up right now. http://www.fatwallet.com/forums/finance/837472

Also, on occasion people post in the forums questions like "How can I turn $X credit limit into cash." Set up relevant topic alerts (http://www.fatwallet.com/forums/alerts.php) and respond by letting them know they can buy gift cards and then convert them into cash on your site.

I'm a regular in that forum so let me know (contact info in profile) if you want any guidance in posting to FatWallet Finance.