[lsc]

eh, I think people tip at min. wage places for two reasons:

1. to look generous/wealthy in front of peers (and to feel generous/wealthy)

2. in the hope that staff will be more friendly/helpful/ won't spit in your coffee.

I think you could apply 1 on line by letting people give you a name to credit publicly for the donation. (let people give you a name; some people don't want to see their real names online)

Applying 2 generally means implementing logins and some sort of 'freemium' model.