One problem which I noticed which was missed by the critical friends (and us, until just now) is that there is still no way to tag your friends if they are only on myspace and you are not. As long as you have a common link (for example one of your friends is on facebook, as are you) then you can share photos across networks but if not this is still a problem.
We see the solution to this as OpenID. ETags can serve as an OpenID provider so that every user also has an OpenID. Users of ETags can then add other ETags users as friends using their OpenID rather than needing to friend them on a network (this would be optional and only needed if there isn’t a common link already).
To provide the contacts list we think we would adopt the open Portable Contacts format which provides an open way of storing an “Address Book”. This is all that is needed by Taggr to ensure that people can tag their friends even if there isn’t a common network between them at all.