I'd have to say it's up to you. I have quite a few great friends that I've met from publishing my PIN. Unfortunately I have met an equal amount of weirdos and jerks the same way. A few weeks ago I had to take it down because men were contacting me and wanting to either talk dirty or get nasty pictures.
If anyone wants my PIN now, they have to PM me and then I can decide if I'm going to give it out. Good luck.
All someone else can do with a PIN really is message you. By no harm if you mean gain access to your phone, no the PIN doesnt do that. If you mean give people the chance to message your phone then yes.