There is merit in some of these ideas, especially if user interaction is simple or essentially seamless.<p>I, like many others, am quite paranoid about giving out my credit card details along with my address and other personal information for both security and privacy reasons, so I would not use any scheme that requires me having to provide this information. That would likely exclude me from schemes where, say, advertisers want actual personal info.<p>A scheme I'd be very happy with would be one where the user buys an anonymous card with a unique ID and a given amount of credit at say one's local supermarket or newsagent and uses the value on the card to make micro-payments.<p>I'm envisioning something like a scratchy lottery ticket where one scratches off a security layer to reveal a code that would be used to make payments.<p>All that's required of the user would be to enter the number into one's browser and that's all. The browser's card management system would keep tally on payments and the credit balance and give the user control over whether to make a payment or not.<p>Such a scheme would ensure privacy and if the card's security was compromised then very little money would be lost—and that loss immediately noticeable.<p>Such a scheme would be very useful in making donations to developers of free/open software (at present, privacy and security concerns and having to enter one's credit card details every time (or for every site) puts a high up-front barrier and it's all too easy for the user to dismiss the developer's plea for a donation).