Purpose of /run/lock/ (empty except for ./whoopsie/)

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http://askubuntu.com – My /run/lock/ directory is empty except for ./whoopsie/. I have understood /run/lock/ as a replacement for /var/lock/ but was surprised to find it entirely empty. Is whoopsie meant as a deterrent from using this directory? I did find other lock files under /run/, though. Most notably in /run/user/<me>/. I would have expect per-users lock files in /run/lock/user/ and not in a separate directory. Hoping for some clarification! (HowTos)