Write on a future resume that you're under NDA about the exact site. Say that you worked on some social-networking site, and give a description of the traffic you got and your role for them. If you know your technical shit, very few companies will care and this lie will work.
This is nonsense. Nobody would realistically ask you to sign such an NDA and having such a thing appear on a resume would look far stranger and raise a lot more eyebrows than the fact you were working for a gay hookup site.
The only hardship you might experience from taking such a job is the ribbing you'd get from future potential employers, partners, investors and co-workers.
That is absolutely not true. My roommate was a .Net contractor for close to 6 years for a firm in San Francisco. He worked on dozens of projects for clients including small firms all the way up to international banks. His resume is replete with entries where he describes what he did but is not allowed to name the company due to the NDA's he was required to sign before working on certain projects.
I personally used to work with a fellow years ago who worked for a server hardware vendor in the north east that had large companies(financial, aerospace) and government and military clients. He told me several stories where he went to non-descript massive underground data centers to do work that to this day he is not allowed to identify. On his resume, he too could only say the type of work he did and could not identify the clients due to NDA.
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.
As long as you know your technical shit and don't lie about your ability, this strategy will work regardless of how illogical you personally feel it is.
Yes, it will 'work' about as well as putting 'I am an unprofessional clown, WIBBLEWIBBLEWIBBLE' in giant red letters on top of your resume. A silly fantasy doesn't become a 'strategy' by virtue of a dozen odd HN upvotes.