as i said before: i would love that somebody comes up with a better study and proves my mini sample wrong, sadly i know none.

i did a similar research of fb enabled signeups vs. non fb signups (on desktop web apps) - outcome: if you enable signups via fb, you get more signed up users.

i think the pro/con fb comments/signups discussion should be based on data (data that is easy to get on our own webproperties) and not on opinions.