Maybe the type of online relationship matters too?
Warning - my opinion only here, folks!
It seems to me that if the relationship is online-only and serious, the play comes as close as possible to in-the-flesh. A safeword would, at some point, be a necessary part of that relationship.
If, however, the online part of the relationship is only supplemental to in-the-flesh, and the play is pretty tame because in-the-flesh interactions are the meat of the relationship, then safewords would not be as necessary.
Edit: Duh! If you're playing in-the-flesh too, you already have safewords set up! Sometimes I just don't carry a thought all the way through...
Does any of this make one single lick of sense?
jeanne