I found a "nifty" bug in CPAN.pm today. If you try to install something gi-normous like Catalyst or Jifty, the CPAN.pm shell craps out halfway through because it deleted somepart of the stuff to be installed during the build for the umpteen billion dependencies.
I didn't track how many modules Catalyst adds to a clean 5.8.8 but Jifty added 174 distributions and eventually failed because of something to do with XML::Parser, WWW::Mechanize, and perhaps some simple thinkos.
Blarg. That's a whole heap of module.