Which brings us to a more complex subject: User-Management. If you have an inventory, then you have unique players. Are the players, their objects, looks, skills, levels etc. saved on your server? Or will the objects be lost after you quit the game?
I think keeping the objects from game to game would be a real reason for people to keep on playing. Of course there should also be games(servers) that only allow “simple” games, whithout any fancy objects from previous games. But the “official” games should have the feeling of a story. Of a player that advances in skill and strength the more he plays. You could also make a ranking of players, giving players a great goal to achieve!