THis is a personal choice, but I simply do not want my details searchable on the internet.
Choose a member of this forum and do a search... you can find out an awful lot about someone.
Combine that with the facility to access your clipboard whilst you are online (Have you copied and pasted your address or credit card details), or do you really want the hostile trolls with your home details?
I chose one member of this forum and now have his real name, profile details on SKy user, London Fixed Gear Forum, amongst others, I know where they work and also Blogger. I have a photograph and know roughly where he lives from some routes on Bikely.
To me it is a simple precaution - If I pm I use my personal details, and when I meet other forummers I also tend to use my real name.
PS I am not a stalker, I just wanted to show what could be done.