The OpenID logins don't seem to work properly? I clicked the G logo to use my google account, but I ended up being asked to create a username and password anyway. Also (at least in Chrome) the links don't have underlines or change when you hover over them in any way, so it's not clear they're links.

Great idea though. I'd like to register but having to update every week seems a bit much. I am usually around my home city, if somebody wants to buy coins from me, that is all the info needed.