Well ... I can see both sides of it. I personally see that as a huge lack of trust and respect between Dom and sub.

That said, one must also take into consideration the fact that the way some Dom's work (as many of the subs on this forum can attest to I'm sure through the unsolicited private messages they've received). Some Dom's seem to believe that they have power over any sub and this could be seen as a way to halt anyone else from abusing the controlling Dom's power.

Much like the majority of BDSM, it's a fine line.