You're right -- some grids are fighting with one another. I guess I should say they SHOULDN'T be fighting one another. Once a person enters the OpenSim metaverse, they typically move around between grids, finding one they like that's a perfect fit.
The big hurdle is to get people to come from Second Life into OpenSim in the first place -- that's where the bulk of the potential new customers are, not poaching from neighboring grids.
Second Life has something like 50,000 concurrent users at any one particular time. This might be down from the 80-90K numbers of the past, but is still more users than log into the public OpenSim grids all month.
And these are relatively easy pickings -- SL users already know how to use a viewer, they've gone through the hard parts of the learning curve. And if there's a tight community of users in SL -- a particular role-playing group, for example -- they can get better service and more land at a fraction of the price.
The super hard part is getting people from outside Second Life to try OpenSim. Companies, schools, non-profits, individual users, groups, and so on.
Any grid that does this is a hero.
I think this is what Kitely is trying to do, with their easy web-based signups and logins, free trial regions, new marketplace, and so on.
And some of the people who try out Kitely aren't going to like it. They might want more of a community feel. Or an always-on map they can walk across. Or more user controls. Or whatever. They can just take their viewer and use it to go to any of those other grids. With hypergrid, they can just teleport over to other grids, try them out, and, if they like them, move there.
And reaching out doesn't have to mean huge, AOL-style advertising buys. Grids can focus on marketing to particular niche audiences, like a vampire grid advertising on vampire-related blogs, buying vampire-related AdSense ads, that kind of thing.
Each one of these efforts might be tiny, but if they bring in outsiders, then they're benefiting everybody.