Measuring effectiveness

MIT Future of Entertainment conference had a panel about measuring effectiveness. The key question asked was "How do people make purchase decisions?". Fallon is reporting about this and I found it funny that the reaction to that question was just a bunch of other questions. No one seems to have been able to present a working solution for the so-important purchase decision dilemma. People talk about timing, convergence of ads and branding etc etc but there is no definite model. One panelist spoke about ethnographic observation as a means to finding that out and obviously the first thing that comes to mind is, geesh, we've had enthnographic observation for 100 years and now it occurs to us that this is the answer. Plus, I have been involved in some projects using that and the best i could tell you is that purchase decision is random and individual-experience driven, and in a world of increasing communication it happens a lot at the point of contact :-)