One of the things I've found with forums is that you can remain as anonymous as you like, but there will always be people clever enough to read between the lines, or do a bit of internet detective work. I've been guilty of it myself.
Have had customers of previous employers contact me through forums, etc to assist with their grievances, even though I've not known them from a bar of soap, saying "Oh, but you used to/or still do work there. You must be able to help me out", or "You c-words f-worded my car!".
It's a pretty small world now that we have the internet.