Oh yes, it's dangerous, and I rarely use it. It's funny, I just cd'ed into my ~/version/loom and saw a directory "58" sitting there dated 2008-08-17. I'll probably keep that one. Then there's "86.12.before_prune" dated 2009-05-20. I could "rm -rf" that one pretty safely, since my prompt shows my current directory as "~/version/loom". Here goes!

  laptop:~/version/loom$ rm -rf 86.12.before_prune

FEEL the adrenaline rush! ;)