The metaverse is an increasingly crowded place, given the number of startups keen to take a slice of Second Life's hype and revenues. We'll be profiling some of the main rivals later this week, as well as taking a look at the hot young guns showing their worlds off at the Virtual Worlds Forum Europe conference. But what about companies who should be launching their own virtual worlds, but haven't yet? I've had a think, and come up with five firms for whom it'd make sense to go virtual. Starting with...