From Facebook Developer Wiki

Suggestion: Can we make this parameter more than 8 characters? We have created our own referrer tracking system, but we'd have trouble adapting to the new system that can be tracked by Facebook, as our current parameters are up to 64 characters long.706757460 22:21, 1 January 2008 (PST)

[edit] Pass app_ref on to the Post Add URL

It would be helpful if the app_ref parameter was also passed on to the Post Add URL request. That way we would be able to track these references on our side as well.

[edit] Does this even work as of 06/24/2008 ??

I've tried using this. I have a marketing and development company, and we are trying to promote an app. We need unique ids to track where the adds are coming from, as we want to promote from our site (for which we are being paid) as well as the client wanting to promote from their site. The method off adding a referrer does not seem to be working, as we've tested and nothing shows up.