daf bit: Nedarim 7

(Today's daf is 11. And way too advanced for me.)

The g'mara is talking about placing people under a ban (that is, excommunicating them) and lifting such bans. R. Abba said: I was standing in the presence of R. Chuna when he heard a woman utter God's name in vain. Thereupon he banned her, but immediately lifted the ban in her presence. This proves three things: (1) one who hears his neighbor utter the divine name unnecessarily must ban him; (2) if a rabbi bans a person in his presence the ban must be lifted in his presence too; (3) no time need elapse between the banning and the lifting of the ban. And R. Chanin said in Rav's name that anybody (not just a rabbi) who hears his neighbor utter God's name in vain must place him under a ban or be himself banned. (7b)

I don't know how, in practice, bans actually work(ed). Sure, Reuven can ban Shmuel, but if neither of them is a notable person, what effect does that have?