There are a variety of tools that live in /bin but are symlinked in /usr/bin, at least on my 10.04 LTS box:

  $ for f in /bin/*; do [ -e "/usr$f" ] && echo /usr$f; done;
  /usr/bin/dumpkeys
  /usr/bin/ksh
  /usr/bin/less
  /usr/bin/lessecho
  /usr/bin/lessfile
  /usr/bin/lesskey
  /usr/bin/lesspipe
  /usr/bin/loadkeys
  /usr/bin/mail
  /usr/bin/nano
  /usr/bin/tcsh
  /usr/bin/touch
  /usr/bin/which
  /usr/bin/zsh

This has the potential to blow something up during the installation procedure if it is not carefully crafted to realize that these files are the same and to ignore link's failure.