Another update: when you actually start interacting with the e-Rewards emails, they start sending more your way. Since I filled out a couple of short surveys, I now get about an email a day from e-Rewards (whereas I used to get about one every couple of weeks).

Still nothing big, but lotsa of 25-50 cent jumps for reading an email and then answering two or three questions. Since we are talking about a tiny time investment (measured in seconds not minutes) and a small carrot at the end of the stick (1000 or 2500 AA miles for me), I will keep clicking for the sake of mild amusement...