Multiplayer is always a big request from players and even if you have highscore lists and chats, people want to see each other.
Yesterday, for the first time ever on Breeder Island, I visit myself on the island :) I set up a node.js server with socket.io and edited my engine so I could broadcast user positions through the net to another instance I was running. If you think "wow, old news, every other developer can do that", you are almost right. A difference might be, that Breeder Island is a web game without flash or any other form of plugin needed to play. For web games, direct multiplayer with up to X players, it is news.
There is a Demo Video available on youtube.
I will keep you updated about my further multiplayer development. The next beta update will rewrite the animal stats system and breeding process, because it is not interesting enough yet.
