I've always wondered about the ethics of this approach. How would I feel if someone told me they're provide an awesome service, took my credit card number and then told me the whole thing was some sort of "customer development exercise"? Personally, I think I'd be a little miffed. Especially if I really needed that service, or was otherwise "counting on it." In the worst case, I might assume the whole thing was a scam to collect credit cards.

Has anyone done this before? If so, did you find that people were generally supportive, or ticked off?