What Key Issues Affect Sales?

[cots]

Here is a discussion topic which has intrigued me for the eleven or so years I have been in this business.

What factors affect sales? Why do sites (including ours) have unbelievably good weeks followed by absolute shockers - from almost identical visitor numbers? Why do some sites work and others not - when on the surface they are very similar? Are the factors "Big Picture" or "Details"? Is it literally the quality/theme of the latest update?

Whilst this is aimed primarily at paysite owners/content producers it would be really good to get some input from affiliates as well. In some ways affiliates have a better view, as they see the broadest possible scenarios and maybe we (paysite owners) get a bit close to it.

Thoughts?