I don't allow .rvmrc .rbenv-version .ruby-version or .ruby-gemset to be checked into the repo. I preemptively add them to the .gitignore even if we don't use them. If developers want them they are allowed to add them with the extension .template. Like .ruby-version.template
I also have a rule of no ruby switchers in production. I firmly believe if you need a different version of ruby on the box get a different box. I would rather deal with server virtualization than with manhandling ruby switchers with capistrano and god. Having no ruby switchers in prod provides another layer of protection for someone adding the latest flavor of the month ruby switcher file into the repo.
Developers can copy or symlink in their local checkout whichever one they want and it doesn't get accidentally checked in and foul everybody else up. It also ensures there are no surprises in production by a developer who isn't paying attention and something sneaks through peer review.
I've also been known to leave angry tirades in comments in the template files that developers should only change them if they are willing to do ALL of the work of upgrading every ruby version in our pre-production, continuous integration, and production servers.
Not surprisingly those files are rarely changed by anybody but me. We have more consistency and no more issues caused by differing versions of ruby between Dev, pre-prod, and production.