YMMV, but we started out pretty ambitious (closest match to our idea was Second Life!), and we had quite a few 'burnouts'. We ended up aggressively cutting off features until we got something playable (people on an island, clicking them around RTS style) and then began adding features iteratively until it morphed into Tribal Trouble. Probably the worst way to do a game, but we were (and to some extent still are) quite green at that time.
There's also the problem of motivation - I don't know if I could make an entire game from start to finish alone without others to show off to or discuss ideas and programming with.