[cd34]

100 hits to a url from the same IP address = 100 RAW = 1 UNIQUE

100 hits to a url from 100 different IP addresses = 100 RAW = 100 UNIQUE

There are three real ways to do tracking:

Cookie
Hash
URL Munging

Tracking by cookie is easy to spot -- tell your browser to notify you of any cookies set and when you click your link you'll see the cookie.

Tracking by hash is usually used as a backup. This is sometimes an IP only or IP/UserAgent hash that is used to identify the sending webmaster. The trick here is that on some 3rd party systems, your hash can get quite muddied by the fact that a user going through one of AOL's edge proxy servers would have the same IP and possibly the same UserAgent as someone else that was sent. I don't know the mechanics of how CCBill does this, but, they do employ a hash as a secondary validation.

URL Munging -- this is pretty easy to see when the url that the surfer sees either has query strings or prestates that follow the surfer along. Provides for an ugly url, but, unless a surfer dissects the url, the tracking will follow through.

Obviously using all three is preferred. #3 requires some work on the webmaster's part to make a tour that passes the info along. #2 requires some database work and #1 is pretty easy to implement without any code changes to the sponsor's tour.