A lot depends on how well you can model attribution. If you're measuring last-click, you're going to see a wildly different story than if you can measure the im

A lot depends on how well you can model attribution. If you're measuring last-click, you're going to see a wildly different story than if you can measure the impact the measure of a impression, mid-stream click, etc. I'd guess most small businesses are not invested in developing stronger attribution models, so looking at Facebook spending vs. something like paid search, as apples-to-apples, is going to make Facebook look worse than it likely is. That's not to say advertisers aren't chasing metrics other than ROI, but just calculating an accurate ROI can be something beyond the scope of many.