To answer the question, no she is not off limits, but she doesn't have to answer anything she doesn't want to.
Was it a rude question, yes, but there is no law that people can't ask rude questions. It was a dumb question in that Hillary's credability is subjective. Some people admire that she stuck with her husband after he cheated, others feel she's dumb for not leaving him.
It's interesting because questions about Monica are going to start happening more frequently. How should Hillary or Bill respond to these questions if asked to them? Be more open and honest about it, or go with no comment?
Also, to Memphis or anyone else, will there be a double standard in the right? Remember when Bush was campaigning, his past drug and alcohol abuse was off limits because "it was in the past". And the **** really hit the fan when Kerry brought up Chaney's lesbian daughter. The right was outraged that he would bring up something so personal. Do you guys think that the right will unfairly harp on the Monica thing?