Successful shooty-guns MMO Global Agenda was a success because it was designed from the ground up to appeal to people too busy with family to maintain a World of Warcraft commitment.
MMOs can't afford to try to be a huge phenomenon anymore - there are just too many of them. As Jim Edge pointed out, you need look no further than recent MMO tragedy APB for an example of what can go wrong when you think too big. Oh, Jim Edge. You are as wise as your beard is long.
Incidentally, I had ten copies of Global Agenda. I was quite looking forward to playing ten characters at once and cackling, but I accidentally mailed them out to ten people who came up with lame uses for jetpacks instead. I'm clumsy like that.
