I've blocked around 20-30 people because I sit in bonfire island.. You probably know "Trolls" hang out there and other annoying people. And that was all in one night. xD But I highly doubt you'll get banned for blocking many people. Have you tried to create a party or a group for your friends and turned off local chat and other annoying stuff? (Local, Movie Clips, and there even is an option in the options to turn off the thing that says _____ has arrived/left/disconnected/lost connection.)