Being slandered or betrayed, mainly by someone I keep close contact with such as an acquaintance, or several individuals. Heck, leaving a bad mark in the community would be my biggest fear. Say, being frowned upon a mass is not a nice feeling, and I hope that would never happen to myself or those undeserving.
Passively, my fear would be embarrassing myself. Though honestly that comes along with my posts quite often, lol
And a fear that is commonly shared along with the other floofs; losing contact with your friends without any other way of contacting them. That would be pretty frustrating.