The default in hiring is no. Confirming the default is a lot of work, and often, you miss a lot of great talent. Here are some situations where I've seen this play out:
NO because of degree requirement. YES candidate wrote the CMS our product was built with. (candidate didn't get job because we found out two years later he had applied and the recruiter never forwarded the resume on)
NO because of 3 years out of industry. YES to candidate because he had the same job at competitor that went public 3 years ago and had a 3 year non-compete (was a CFO, so it was real). (recruiter had a policy of I talk to every applicant, and the candidate told her who he was and why he applied... hired)
NO because of multiple 1 year gaps in employment. YES because candidate had managed multiple five year construction projects on time, on budget. Turns out the gaps were where they guy took one year off and volunteered, helping build schools in Africa. (recruiter sent to hiring manager, and hiring manager passed because he thought the guy was a "job hopper")