I work for a company with well over 100,000 employees, but if I gave my salary, title, and years experience (and as someone else noted, especially if I added my location), I wouldn't be anonymous. To my employer, at least. It would be trivial for them to narrow down the information to being provided by a very small number of people - if not the exact person.
I don't see this flying, where I work though. Even among the people I'm closest to, I don't think they'd take to this sort of information sharing amongst each other. Even pseudo-anonymously. I'm not sure if that's because they'd feel it's tacky or if it's because it has been drilled into everyone from corporate culture that you _never_ talk about it.
As an aside, I would actually much rather know not what the guys I've been working alongside for the past decade are making compared to me, but what new hires in the same positions as us are being hired at. Especially when you throw in all the hiring freezes and pay freezes over the last ten years.