I am a member of a site that requires all its members to link to the site homepage.

They have just asked that we append a variable to the links so they can monitor inbound traffic more accurately, so the links will now be of the form
www. mainsite. com/index.php?ref=12345 (with a different id for every member)

I was concerned that this will make google think there are lots of 'different' pages but all duplicates of each other - so they benefit of the inbound links will get spread across lots of identical pages.

Any thoughts? Do I need to worry?