Occasionally there is a dispute over who "owns" a callsign, and one of the parties involved refuses to accept a duel to settle the matter. I was "eagl" since early WB ("suck" before that in CK) and some guy came on with eag1 (eag'one'). Of course I had to duel him for the ident, fortunately he was a good sport about it, and fortunately I won the right to keep the callsign.
The point being that if someone takes your callsign in the arena or forums and isn't big enough to duel for it, then you might get stuck.