How could recurring payments be implemented?
I think the most obvious way, though perhaps not the best way, is precisely the same way as is done with other currencies. If Bitcoins are adopted as a primary currency, they'll probably be used the same way other primary currencies are.

I am paid in dollars, but no actual dollars transfer unless that is absolutely required. Instead, I have a bank account denominated in dollars from which I can withdraw actual dollars any time I need. These same mechanisms could be implemented with Bitcoins. I could have an account denominated in Bitcoins, I could be paid in Bitcoins, I could pay bills in Bitcoins, but no actual Bitcoins need change hands except where the benefits of doing things that way outweigh the costs.