This is clever technology and a well-known problem, but I wonder how much traction it will get since it's going to be a for-pay service.
Better for the company to market themselves with - create their own repo, but Open Source it and make sure their URL appear in every aptitude run.
Here is the official position of the Debian/Ruby-Extras team: http://pkg-ruby-extras.alioth.debian.org/rubygems.html
It has been a polarizing issue, as you can see.