I insist on credit cards upfront on moustachecoffeeclub.com I am sending people a free physical bag of coffee though that costs me around $12 so it's very important that I convert people. But yes, lots of advantages to this approach not least getting rid of time wasters, who always seem to be the most annoying "customers" on the planet :)

I think I might do a post sometime about all the fun ways I've sacked my annoying customers. Keeps me interested anyway :)