I think proposition #2, ala flattr, is the only viable one out of this lot. The other three all fall on the sword of "should I pay $0.05 for this mouse click?"

I think proposition #2, ala flattr, is the only viable one out of this lot. The other three all fall on the sword of "should I pay $0.05 for this mouse click?". If the user ever has to ask himself that question, the game is up.