>I've never once seen this question asked on a job application
>or anything. I've successfully gone through DoE Q clearance
>(equivalent to a DoD Top Secret, but dealing with nukes
>instead of military/defense). I've had several FBI background
>investigations done. This shit was never an issue.

The FBI says they consider an applicant's criminal history when reviewing an employment application:

https://www.fbi.gov/news/podcasts/inside/background-checks-for-new-applicants.mp3/view

Mr. Gant: “The issues that we’re looking at for suitability involve candor issues; individual’s use and/or abuse of intoxicants; >>their criminal behavior<<; personal conduct; financial considerations; and employment histories. As it relates to security issues, and we utilize trying to verify a person’s date and place of birth; their citizenship status. We check FBI files and other agency checks and we also verify education, employment, organizations that a person belongs to. We check their references and associates; their relatives; associates and roommates; check their marital status and then try to also assess their associations in their neighborhoods, trying to find out if this person is a true and loyal citizen of the United States.”

https://www.fbijobs.gov/are-you-suitable

Employment Disqualifiers
There are specific elements that will automatically disqualify job candidates for employment with the FBI. The FBI Employment Disqualifiers are:

Non U.S. citizenship
>>Conviction of a felony<<
Use of illegal drugs in violation of the FBI Employment Drug Policy
Default of a student loan (insured by the U.S. Government)
Failure of an FBI-administered urinalysis drug test
Failure to register with the Selective Service System (for males only)

Please note that if you are disqualified by any of the above tests, you are not suitable for employment with the FBI. All of these disqualifiers are extensively researched during the FBI Background Investigation Process. Please make sure you can meet FBI employment requirements and pass all disqualifiers before you apply for an FBI position.