People tend to think of evaluation as something you do at the end of a campaign. In fairness, doing a full evaluation at the end is a massively important part of any campaign strategy. But it’s also helpful to evaluate as you're going along. Lots of brands make the mistake of closing their ears to ongoing issues and save any feedback for the end of campaign evaluation.
That isn’t to say that sales-y promotions couldn’t ever create results—as marketing “gurus” have proved. The results just aren’t as good as they could be. Take the biggest gurus’ results—the ones they boast about—and calculate their conversion rates. Often their marketing is comparatively ineffective. They just have massive volume, so the sales numbers are impressive.