I tend to use the same username a lot... But I don't necessarily stick to it everywhere I register. Some sites I don't use a name connected with me at all. (Especially if I'm doing post exchanges... This way it's less likely that a prospective member is going to see my name and know that I'm only there as part of a post exchange. Even other members from here seeing it might not make the connection. Which looks good for the forum in question because then at least it appears like it's not just the same groups of people from FP. )
You will only see "Faker" on FP, I made this account when i was doing GFX and "Faker" is my GFX Name. Nowadays when i sign up on a new forum i go under my real name Chris or Christopher.
It depends for me. If I think I can and will stay long in a new forum I'm joining, I usually use my current user name. It is my first and best user name after all. However for certain situations I prefer to hide and use another name, until I'm sure enough that I want to use my 'real' user name. ^^