I will reveal, personal details to a point. I will only give such information as I would normally give on meeting a person, for example my real name and age, which I have posted on these forums before, for those that missed it my real name is Chris and I'm 23, also people will be aware that i have 3 children and l live in Lincoln, i see no issue with people knowing the city I live in as long as I don't plaster my adress all ove the internet, In fact another forum I am on has my real name as my username. Beyond that I will never give out further details online (after saying that I beleive my date of birth is on facebook which I seldom use). But there can also be problems when someone with a grudge takes your username from a forum and uses it to post unsavory things elsewhere, this actually happened to me where someone I had a long standing disagreement with (going back to school), discoverd my username from this forum and posted some frankly disgusting comments on an article on my local newspapers website.
Its horses for courses really, everyones view on what, and what not to reveal online will be different.