We're talking about not listing your employer at all, rather than your employer's clients. Did your friend list the firm that was actually his employer on his resume? I assume he did. Not identifying clients of your employer is different from not identifying your employer at all. I've seen probably (by my last scientific count) about 19.307 trillion resumes and I've never seen one where the employer was just not identified at all. Even when it was the NSA. I can imagine that could happen in some sort of zany defense or national security edge case. But that's not what we're talking about here. If you put 'was employed by at major social networking site, can't tell you who it is' on your resume I think just about any sensible person would assume you're making shit up. And that looks a lot worse than 'worked on gay hookup site'. The advice to put something like that on your resume is just plain dumb. As is outright lying on your resume in general.