Alexandre,
Definitely like the idea, and is similar to something we're already partially planning. We're just starting a plugin which will add "Connect this account to: Facebook / LinkedIn" to the user's My Details pages, as well as letting the use 'break' their connection between their accounts. The plan is to start enable an automatic integration into a few more places more easily, and I think we could do something similar to the standard Joomla user login page automatically as well. Hadn't thought about that portion, but would definitely help users out a bit instead of some of the manual things that may be necessary now.
Really like the looks of that page though, and you sold us on the idea.. now just to do it
Planning to release JLinked v1.0.0 next week. Excited to see it on some sites now (with not too many issues!)
Thanks again for all your feedback!
Alex