I came across this blog entry and was quite surprised by it:
http://blogoscoped.com/archive/2009-06-12-n15.html

"It seems that even if you choose to skip the contacts you have imported [using the webmail or contact list import tool], Facebook will still store your relationship with those contacts. Not only will it continue to include them in your suggestions, but it will also alert them to the fact that you previously imported their email address and that you are registered on Facebook. Facebook clearly states that it will not store your password, but it doesn’t tell you that it will store all your contacts even if you chose to skip them.

Admittedly, your account will only be suggested to others if your privacy settings allow your profile to be returned in search results, so anyone could search for your profile themselves, but is it right for Facebook to suggest you to the people that you have chosen to skip? Also, does this mean it’s possible to force yourself into someone else’s suggestions list by simply adding their email address to your contacts?"