This week saw Neverdie Studio launch a new virtual world: Rocktropia, a music-themed world for rock fans who want to indulge in heavy metal fantasy. Users can log in, deck their avatars out in rock star fashions, explore an album... More...
interesting clippies "where players can go on quests to earn in-game apartments" "The world can support up to 1000 users in any given area. ... goal is to build the platform out such that it can support 50,000 simultaneous users."
I'd say 1000 is a stretch. Perhaps if not all of them are in the same location, but the game pretty much becomes unplayable if there's a few dozen avatars at the same location.