I've not really frequented them, but I have it on good authority that League of Legends' public chat rooms are pretty nasty. Whose, you ask? Why the authority (named for a total lack of authority) that matters most in this case: Riot. They're so fed up with what public chat (read: non-private rooms; those have mostly taken its place) has become that they're yanking the cord altogether. For the time being, anyway. Big upgrades are needed to keep away griefers and spammers, so Riot's taking the necessary time to send them packing.
Riot laid out the problem in a quick blog post:
"The official public chat rooms have grown rife with RP sellers, scammers and Elo-boost spam. The default four rooms we established can be used by a tiny fraction of our players at a time. Given the number of League players, most conversation spills into private, community-created rooms."
"Unfortunately, private chat rooms and even the awesome community hubs like Dominate Dominion and Summoner School lack moderation tools beyond the ignore button. While the experience in private chat rooms is better than the public versions, we still want to provide tools to address unwelcome drop-ins and toxic behavior."
"As an immediate action we’re going to disable the public chat rooms until they’re useful and accessible. In their current shape they just don’t work and can actively create negative experiences for many players (especially new players)."
Private chat rooms and messaging, however, will remain unaffected for the time being.
In the future, Riot hope to have chat channels, hangouts, or whatever they end up being called for all sorts of topics - persistent spaces for people to gather and chatter about anything from jungling, to mentoring, to champion theory-crafting, to casual ARAM, to ranked games.
Right now, however, the tools aren't good enough, and Riot fully admit that. So continues Riot's ceaseless crusade against toxic community shenanigans and those who might take advantage of their fledgling multi-million dollar economy. I wish them the best of luck in that, though it's one heck of an uphill battle. Online communities, you guys. When I first signed up for this world-wide communications web thing, nobody told me I'd have to deal with other people.