A referred click would be a click through going through our referral script. We can track a sale back to a referring account if it doesn't go through our referral script. As you pointed out, you know what tracking is and how it works... Go off that knowledge base.
The 0.5% that didn't get referred yesterday would be based upon server errors, net errors, user errors, scripting errors, DB errors, a huge list could follow but you get the point. Our systems are very accurrate.
Also, your comment on generating traffic or SE work - you simply use another internal account number.
slapass - a big site makes things easy... ARS had 3 big sites, Adult Movie Station, All Petite, and MILF Search
Right now we're doing big numbers with XXX Teen Tease and Chicks Go Both Ways.