What's the default Ruby version on OSX Mountain Lion ? Still 1.8.x or 1.9.x ?
On Mountain Lion, it is Ruby 1.8.7-p358 (Tested with OS X 10.8 and 10.8.3):
$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.8.3
BuildVersion: 12D78
$ /usr/bin/ruby -v
ruby 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0]