When I got our DROID's yesterday I set up both phones (myself, spouses) with the same gmail account, which was my gmail account was a huge mistake.
Because it was set to sinc with all, email, contacts, calendar etc, whenever my wife would enter her contact info, I would get it too...it freaked me out, but then I figured out that all I had to do is reset the phone, but before doing so, I made sure I backed up all her contacts in a gmail format for export.
I created a gmail account for her, since she didn't have one, and imported all her contacts into her account. When I was finished reseting her phone, I logged her phone in with her new google account, and pressed sinc and walla...just like magic all her contacts returned, because after reseting the phone everything was lost.
That was a great learning curve for me...I'm glad I went through it since troubleshooting and fixing is my life..ha,ha....
As for the gmail problem I don't have an issue with it showing up on all my other gmail accounts. it may be just an issue of the number of gmail accounts listed on the phone.