Apparently, this uncommon syndrome is prompted by situation the people find themselves in. So, it is not a syndrome the sufferer are aware of. It's something that develops as the hostage becomes helpless in the face of threats rain on him/her by the captors.
Agreeably, it sounds bizarre to know someone that is holding you captive is the same person you're having a soft spot for. I read that some of the hostages can even go as far as assisting their takers to negotiate for their demands for their agenda to be met. Obviously, the affection such victims have for their captors have psychological undertone.
More importantly, such bond established in the stockholm syndrome is occassioned by the situation on ground. I also think it's as a result of the time spent together by the hostage and the taker. Or perhaps, it is survival strategy to escape from the fury of the captors.