If a player's connection lags, and he keeps trying to spam pass host in the meanwhile (10+ times) he'll get silenced for spamming in #multiplayer. Probably has to do with too many packets sent to Bancho, which is understandable, but it would probably be better to limit it from the client's side.
I have not personally been silenced myself due to multplayer socalled spam, although I have experienced slow internet connection, and I have to spam to make the host rotate indeed.