I believe that since a sub is willingly giving control to the dom the "Stoclholm" syndrom would not apply. There is a huge difference between starting out as a willing participant and being put in a situation where you have no choice at all.

In BDSM the sub should be a willing participant, getting pleasure by surrendering control. The opposite, whether kidnaping or abuse, presents nothing but forced control inposed by another. A totally different matter entirely.