That is the second plant I have seen in a week with exact same results. White hairs coming out of balls, someone in the 32oz grow thread had one last week as well. Almost identical.
To answer your questions:
2) Should you be worried about other plants in the tent. Possibly, there is no 100% positive answer. If it was stress than there is a chance the others were stressed as well. Have your temps been real high or low? Have you had a big ph swing? Overfeeding episode or anything that would have caused undue stress? I doubt it from what little I can see of the plant, it looks picture perfect. If it were stress then the others could hermie. Could it have been a bunk batch with genetic disposition to hermie? Possibly, if that is the case then the others may hermie as well. Short answer is, I wouldn't worry but I would keep a very close eye on them. Checking at least every other day or so.
3) Hermies will not affect potency. That is highly debatable and opinionated but from my experience hermies, even if they pollinate the plant will not affect potency. It will effect yield though, the plant will begin using energy to produce seed at that point.
There is nothing to worry about! There is actually less to worry about. You know what you are looking for and you caught them very early on. If you continue to see balls pop up regular then you may want to consider starting some new beans. if it does continue, then when you get into heavy budding you are going to have a hard time finding them because the bud sites can hide them at times. If it does pollinate then definitely do not keep the seeds. If they are genetically predispositioned to hermie then they will pass that trait along to offspring.