Spam notwithstanding, what's wrong with the usual methods for sorting email, e.g. catchy wording in title, and filtering based on whether the sender is familiar to you?

Admitted I'm not a celebrity like Arrington, but I really don't find myself especially more likely to absorb email content that I'm apathetic about, even if I get paid. And precisely because I'm no celebrity, I don't see how I could be paid anything more than a pittance by this scheme, meaning someone would be buying my attention span for very cheap.

I'll let the attention span devoted to writing this comment (provided free of change) serve as an example of how I believe this scheme would drastically de-value email readers' time.