This is the one situation where it does work better. Many years ago I was interested in affiliate marketing, where there was a relatively immediate purchase.

This is the one situation where it does work better. Many years ago I was interested in affiliate marketing, where there was a relatively immediate purchase. The aim then was to optimise spend and conversion rate and a profit could be eeked out. When there is a slower sales cycle and a more complex or less transactional purchase then it all becomes much more vague and significantly harder to find ROI in my experience. The ad-click is likely to be one of a hundred factors compared to transactionally selling a widget.