I used the Ruby code at the beginning of http://stackoverflow.com/questions/16323571/measure-the-dist... to calculate the distance between the package names at page 60 of the thesis and their typos.
The maximum is 2.
I checked some similar package names from a Gemfile.lock of a project of mine. Unfortunately the two gems hike and hirb are also at distance 2. Probably many short names are close with this metric.
A combination of the two approaches could be ok: knowing that a name was blacklisted should be an indicator that's not a good name, despite the distance with any other name, plus an approval of the maintainers for distance 2.
But a blacklist could generate another type of squatting, with people trying to pre-blacklist perfectly legit names. Only one thing is sure: there is more work to do for the maintainers and this extra friction is not good.
Edit: the distance suffers from the same problem.
I see what you did.