I typically try to route my customers to the anonymous checkout route, since it helps avoid confusion (remember passwords) and essentially you still gather all necessary information and an email without having them feel obligated to "Create an account"
However, given some of the more open protocols for authentication coming into the mainstream, I'm curious if anyone has added Facebook SDK login or OpenID to their nopCommerce?
And if so, would they be willing to share?
I think this might help encourage users to "interact" with the store a bit more and also share a bit more information, that I could than use to later reach out and touch past customers in a different way -- via updates on Facebook, or twitter V.S. email marketing!