Every merchant should create keyword lists for affiliates to work from. A keyword list helps both PPC and natural search affiliates. By defining themes you can reap traffic benefits that your own site does not focus on. For instance you may sell Ipods and accessories but you cannot expect to hit every keyword or phrase and be in the top spot. Have your website focus on your branding, customer service, unique sales proposition and user-friendly content.
This is good advice, thanks. It is important to be focused, if you're too all over the place then you wont bring in the revenues you are hoping for.