Who'd be a GM? If you don't fill a dropped position you've done
something wrong and when you don't try to fill it, guess what? Yup,
you've done something wrong! 
*However* ...
I hate to say it, but Gavin has a point.
If I was in that game, I'd be very pleased to have that information.
Such details should NOT be given out publicly ....
True, but Clint obviously has to try and find new players for such
positions. I wonder if there actually is a list of players willing to
take on stand-by positions? At the start of every game there is a sheet
attached to the back of the order sheet which asks if you'd like to have
your name put down on such a list. Whilst most people probably never
return this, I believe one of the past GM's (Matt probably) used to
contact people directly whom he knew might take up a dropped position.
Obviously this takes more time and care needs to be taken not to contact
people already in the game, but it's probably better than generally
broadcasting the fact.
If the game was being played *properly*, i.e. there was a team, whether
at gamestart or one that developed during the game, then of course this
wouldn't be a problem as it would be up to the team to find a player!
Colin.