[rendx]

A "flag content" link should be good enough. Sounds like you're US based; you're not required to manually check all user-contributed content. Set up a DMCA section and link to it at the bottom. If LEA contact you, make sure you react fast, and maybe you want to offer them an automated way of takedown if this really happens that often.

For the future: Asking legal questions without stating your jurisdiction is... not helpful. :)

Yes, big sites employ a lot of people to clean content. I remember reading an article about poor people in $third_world_country that do this all day long.

[VexedSiteOwner]

If you can locate the article, I'd love to give it a read.

I'd rather keep my money inside US borders, but it ain't cheap, and staring at the sickening contents of the internet's collective wet dream ain't exactly a high-profile career path for young folks.

[rendx]

Here's one: https://www.wired.com/2014/10/content-moderation/

"Hemanshu Nigam, the former chief security officer of MySpace who now runs online safety consultancy SSP Blue, estimates that the number of content moderators scrubbing the world’s social media sites, mobile apps, and cloud storage services runs to “well over 100,000”—that is, about twice the total head count of Google and nearly 14 times that of Facebook."