I recently published a Forrester report titled Marketing's New Key Metric: Engagement (more detail here on the Forrester Marketing blog). One interesting aspect of this research was presenting the idea that the marketing funnel is more complex than we may think. I initially presented to my fellow marketing analysts an idea that suggest the funnel was dead. That didn't go over so well, which demonstrates how sacrosanct the funnel is to marketers. However, they also presented a good point that the current funnel (awareness, consideration, preference, purchase, loyalty) is meant to provide a framework for marketers to understand all buying decisions at a meta level. With that, I proposed, and published, that the funnel is more complex, not necessarily dead. The point here (see graphic below) is that the center of the funnel is a lot more complex now. There are a lot of addition factors impact a person's decision making process.
Another insight here is that we need to think differently about what a 'valued customer' is. Traditionally, we think a person that buys a lot from us (at a profitable price point and not necessarily at discount) is a good customer. We through in other factors like frequency and dollar value of purchase, but overall it's about buying. However, one of the ideas I present about engagement is that someone that contributes content that influences others to buy (even if that creator doesn't actually spend much with you) could be extremely valuable. If someone only buys from you once a month, but every time they buy they write an extensive product review that increases the likelihood that readers of that review will buy — that's a valuable person too.