There are 3 important things to remember when discussing attribution in the Affiliate channel vs. PPC.

1. As you pointed out – the Affiliate ad may have been visited some time ago (an account setting) and could be 15 or more days prior for example. Affiliate programs are told to track this to an affiliate…so they do. Affiliate programs typically are charged with looking at the last “Affiliate” click, not the last “overall” click. So the last referrer, while it may show a Google search, may not be the last Affiliate referrer. Both can be correct.

2. Affiliates are not paid anything on a per-click basis. So, while all of those other campaigns (PPC etc…) cost a Merchant money on the front end…. the Affiliate relys on the conversion for commission. That is one of the reasons that the 15-30 or even 60 day delay is used. While the issue of attribution is important, it is also critical to remember that those Affiliates that are out there promoting Merchant’s products are doing so essentially for free until a conversion takes place. That makes the interpretation of the metric entirely different from a PPC ad. While one may see a single commission and look at it as a greater cost – failure to remember that the previous 100 clicks were free is an important error.

3. Affiliate commissions can be voided, adjusted, or in extreme cases the affiliate can be removed from the program if continual evidence of channel conflict seems to point to the affiliate.

Imagine what would happen if you requested money back from a PPC search engine because you felt like there was overlap in the channel… Affiliate Marketing allows greater flexibility and allows for these kinds of things to be researched and properly corrected.

There are no totally accurate analytics programs and the best do usually cost more. I’ve been meaning to do more research on the best options for bloggers and affiliate marketers.
Internet Strategist @GrowMap´s last blog ..How to Optimize Your PPC Advertising to Benefit YOU

Even if the analytics programs started tracking every click there is no real way to know which affiliate had the most impact. It is likely that the last affiliate closed the deal so last click is probably better for affiliates than first click cookies that have really long durations.

Either way, that should average out over the long run for affiliates. Affiliates have to know that they simply are not going to be paid for every sale. Perhaps educating the public on the value affiliates provide would improve the number of sales affiliates earn commissions on.
Internet Strategist @GrowMap´s last blog ..Success IS a Numbers Game