The MS login popup shows when I add www.so.cl to Trusted Sites in IE9, but not until then.
The FB login popup shows without having to add the site to Trusted Sites in IE9.
Chrome has not got this BUG, others just proved to me... it's an IE9 special.
EDIT: and I still suspect shennanighans where FB data collection is the goal. Nasties for that if true.