Hm... I thought this is a virus, because it was constantly (several times per day) showing notification like "Your FB session has expired, please login again", and if I tap the notification - it would show a "login page". Surprisingly, I could continue using FB at the same time without problem.

This looked like an attempt to steal my password, that's why I disabled this stupid SNS, but there is no possibility to delete it.
Now while looking about what is this app and how to remove it easily - I find this thread which says it's useful good app. Hm... I still doubt it.