
Originally Posted by
http://gmail.google.com/support/bin/answer.py?answer=10959&topic=42
Why are there addresses in my Contacts list that I don't recognise?
Answer:
When you send a message to someone new, Gmail automatically updates your Contacts list with their address. Gmail also updates your Contacts list to include the address of the person who invited you to create your account.
You can't disable this feature, but you can remove addresses from your Contacts list at any time. Here's how:
1. Click 'Contacts' along the left side of any Gmail page.
2. Tick the box next to the contact you would like to delete.
3. Click 'Delete' at the top of the page.