I like OgNasty's proposal, although I do agree with others that 2BTC is a fairly high barrier. With my current sig campaign, that would take me 20 months to earn. I think something between 0.75 to 1BTC is more reasonable and more attainable.
Wrong. The more you lower the amount, the more spammers you are letting through. As a normal user that tries to engage in discussions and help others, you don't need a signature (if you can't pay for it).
Only in Bitcoinland do people complain about a 20 month ROI. Rest assured that signature campaigns would have to pay more.
Exactly.
There should be no ROI at all.