If I were to choose one most commonly recurring problem with websites that run affiliate programs it would be leaks. In brief, a leak is a path to an untrackable action that the end user may make bypassing the route that provides for an affiliate remuneration.
Affiliates are in this business to make money. They are also being remunerated for their marketing efforts only if an action (a sale, a lead submission, etc) takes place.
Every e-business that starts an affiliate program must become extremely sensitive to the fact that once the program goes live some of the traffic will be sent to the business' website by marketers who are paid on performance basis only. This should get translated into becoming respectful of affiliate marketers' efforts, and removing any possibilities for the visitors they refer to "leak" without completing the desired action.
There are 5 main types of leaks that merchants are prone to:
1. Telephone Numbers
This is by far the most frequently recurring leak. Unless the merchant offers a solution to track phone orders, every affiliate-referred customer that places the order over the phone means lost commissions for affiliates. Here are two examples:
Both of the above merchants run their affiliate program on ShareASale, the network that does offer merchants a phone tracking solution. The solution has not been implemented, but the phone numbers are prominently displayed in highly visible spots, even when the visitors arrive to these websites through affiliate links.
2. AdSense Units
Vast numbers of merchants are running these on their websites not realizing that by monetizing the affiliate traffic in this way, they are cashing in on affiliate efforts that are really geared at marketing their main product/service. Here is just one example (I've picked this one because of the prominence of Google Ads on this merchant's website):
3. Amazon Widgets
Quite a few merchants also have Amazon's widgets on their websites. Yes, I do understand that these books are directly related to what you're selling, and with your target audience you're probably registering an excellent conversion rate, but are affiliates who are referring visitors to your website benefiting from this at all?
Here's an example of a merchant that has an Amazon widget on their website:
4. Links to "Network" Stores
Some merchants list other websites that they own, but overlook the fact that once the affiliate-referred visitor "leaks" to those websites, there is no chance the affiliate could earn any commission on his/her purchase in that other store. Same applies to Amazon stores and eBay stores that merchants may run. While in the example with the sister companies it is possible to make the tracking of all orders across "network" stores possible, neither Amazon, nor eBay sales can be tracked (they won't implement your tracking pixel on their "thank you" pages).
Here's an example:
5. Affiliate Links & Links to Other Merchants
Finally (believe it or not), there are merchants that also wear an affiliate hat, displaying affiliate links on their websites. Here's one:
If a visitor that an affiliate sends to the above website, books a limo, this merchant will get their commision, while the affiliate will get nothing.
Another variation of the same type of leak is direct linking to another merchant's website.
Many of the above leaks are caused by the merchants' ignorance of the consequences. Hence, this post.
Respect and reward the work that your affiliates are doing for you, and they will respect and reward you in return.