I think the only thing applicants should hide is whether they have a mental illness of some form. It's probably legally best to hide medical information anyway; it puts interviewers in a tough spot.

I've never had an issue with a gap. Sometimes relatives get sick. Sometimes they go on a 3 month road trip on a bike, or a pilgrimage. Sometimes they try to start a business. None of these are negative things. Sure, some guy might be in prison or rehab, but that might not really matter.

Whenever we see catch a lie on a resume, the interview is over.