smallcompany - 1:39 am on Jan 10, 2013 (gmt 0)
I used my own affiliate links to order merchandise and services. Some webhosting companies do not allow it and they filter it out by name (I did it and asked).
I know some other that always paid me. Those I bought merchandise from, it was always tracked.
I agree with the claim that in many cases they simply do not implement tracking code properly (or at all). With some, it always happens whenever they do some kind of update.
Also, I'm sure that some do it on purpose. How, I'm not sure, but they hide some of sales as that's in the nature of some people.
For networks, they don't get paid if sales were not tracked, so it's definitely in their interest to track all sales, period.
Then, I worked with advertisers that would leave various networks for their own reasons, and pay me outside of those networks.
Finally, all of various software that overwrites cookies... I don't know much about that but it obviously is happening in one or another way.
In any case, it really sucks when an affiliate finds out something like that (especially if you're doing paid search). Since a day when I started doing this (back in 2004), I have always been a skeptic thinking I'm underpaid in one or another way.