This is a problem when noone wants to lead though.
Here at my company we tried to make a pre-A round of sorts (mostly because we are in Brazil, and investors here are unwilling to invest anything close to a A round here).
We had several people commit saying that if other people go, they will go too... But we found noone to commit as leader, and all the other commited investors refused to go without a lead investor, kinda annoying situation.
Happily our seed investor liked our recent results and expanded his seed investment instead.
All it takes is for someone to cross the bridge of commitment and others will follow. The fact that I'm probably two orders of magnitude poorer than the other investors probably helped in embarrassing them to make a move, it was literally peanuts to them and the company went on to moderate success.