As this is on the DIR thread I thought I'd chip in.
Boltsnaps should be attached using caveline, not using somethinglike an O ring. the DIr standard used to include a breakable connection in this way, but iut was found not to provide any real advantage, and as they degrade over time they can provide a disadvantage over using caveline. thus the standard was changed so that all boltsnaps should now be attached with caveline.
The reg exists basically in one of three states. It is in someones mouth, clipped off, or in someone'e hand, so it is never left dangling. The reasons for this as Digger has pointed out, is that it can dangle below you without you noticing. Perhaps more dangerously, it can get caught up in something and snag you, even ending up behind you where you cannot reach it. I have actually seen this happen.
How to tie a suitable knot can be seen here
http://fue.no/fue_mambo/index.php?op...1&limitstart=3
And the boltsnap should be placed right next to the second stage.