While I know it's easier to just '@set me=unfindable' when faced with the bad apples, the more appropriate choice of action is actually 'p staff=Hey, so and so is hassling me about being in a private place with someone else. Can you let them know it's not cool?' (better) or 'page creeper=Hey, when you bug me about who I'm playing with it makes me uncomfortable' (best).
Yes, the flag is an easy solution, but it's also an incredibly passive aggressive solution that does not in any way, shape, or form deal with the problem, but instead addresses the symptom.
Unfindable enables passive aggression. It also enables those bad apples to go 'oh, no, I had no IDEA who the person was playing with, she's unfindable, I didn't see anything' and makes cheating along these lines much more difficult to address.
Harassing someone about playing with another person? This is generally against the rules on any given game; the key in this one is the word 'harassing'. Using OOC knowledge (obtained from +where) IC when this sort of thing is not permissible? Against the rules, the key for this one being 'cheating'.
Make (and enforce) rules that actually address the problems themselves, not the symptom. If you have some guy paging people with links to him jerking himself, the solution is not to @wall for everyone to please pagelock themselves. See?
ETA: tl;dr: All unfindable really does is let assholes keep being assholes.