Sorry to hijack, but I've long had this idea, and possibly offer it to people here for stealing, but mainly want feedback on whether it'd be worth implementing:

You, the creator, make some content available for download. You only require the visitor to give you an email address, optionally requiring validation. The visitor then downloads and consumes the content. After some amount of time, configurable by you, the visitor gets an email saying "hey, if you enjoyed my content, please click here to pay me the recommended $X, or ignore this email to be notified later, or click 'no thanks' to never be notified again". Basically, paying after the content was consumed, but not so much later that they've forgotten about it.

What does everyone think?