It's not the same in the world of Federal/Military security clearances. For a Top Secret they'll go so far as to dig through your personal life, medical records, police records, school records, contact friends of friends, looking for anything that may suggest you're not 100% trustworthy.
Exactly - that's what my answer was predicated on - that this was a background check performed in connection with Federal Government and/or Military clearance. Even there, while an
arrest, by itself, isn't an automatic deal-breaker (except in certain very highly sensitive TS/SCI or TS/SAP cases where it may very well be) but you can be sure that it will be closely looked into and it may come back and bite one in the ass.
Of course employers are free to use whatever criteria they want in evaluating employees (except for what the law explicitly forbids them from evaluating) so a prospective employer could probably even
require that you have an arrest record in order to be considered. Arrests probably aren't that big a deal for most civilian background checks; sometimes even a criminal record isn't a deal breaker. For example a lot of people with records end up getting jobs in the computer security sector; Personally, I see this as both good and bad: on one side I don't want to penalize people for stupid mistakes in their past, but on the other hand I don't think it's a great idea to have someone whose business card says: "Chief Security Officer, Convicted Felon".