What about clickpass? Although that might be subject to trust issues too. Most users are familiar with the verification concept, although still don't like it.

What about clickpass? Although that might be subject to trust issues too. Most users are familiar with the verification concept, although still don't like it. Can you explain why you need a valid email address to do payments? Just allowing Google accounts limits your market somewhat, but if you are going for techies first, then you should be fine.