It's a concept that has been around in various forms for some time but doesn't seem to have gained much traction anywhere. As well as a tip everywhere system I assume your letting publishers after they have claimed their site to push the tips with buttons on their site?

I don't think I would be inclined to ever tip unless I knew that the author has a presence on the tipping service so I knew they were actually going to claim the tips. Wonder to if a reverse model, similar to a kickstarter would work, as in an author proposes a piece of content they will put some time into a produce if they get some upfront commitment of tips.