To answer your question, I have not seen it for a while.
However, I have been migrating away from Centos to Ubuntu, so that may change this. I have only a handful of Centos servers remaining. In addition, those are much less dependent on gems as well, so I'm running few to no gem installs on Centos lately.
I have not observed this behavior on Ubuntu where I do have a lot of gem installs occurring.
A conversation has been started with the RubyGems.org staff to resolve this discussion.