Search is a fantastic marketing channel. If you know what you’re doing (or you hire an agency to do it for you!), the ROI can be huge. Facebook advertising can function much the same way, but you (or the client) need to be aware of its differences.
Facebook advertising can perform similarly to other performance marketing channels, but it’s also inherently a bit different. Social is typically more volatile than search (people targeting vs. intent-driven targeting) and can have peakier peaks and deeper valleys day-to-day. To mitigate mini to major freak-outs, be sure to always look at data in 7+ day increments to measure trends. Anything less, and you’re just not getting enough information to make an appropriate decision.
Similarly, Facebook advertising takes a bit of time to reach a point of real consistency. The first month will have many ebbs and flows. Expecting immediate efficiency and consistency (like you’d get from a search account) is just setting yourself up for heartbreak and anxiety. One reason for this is the maturity of the respective platforms. Search is “old” in terms of digital marketing standards, while Facebook is a relatively new platform. Reaching equilibrium requires a bit of trial and error because of a lack of established best practices. You’ll get to the correct place at the end, but the paths to get there will vary based on marketer experience and the type of account.
You’ll also be dealing with external influencers that you don’t have to deal with in search: comments, shares and other social signals influence the reach of a post in ways that simply don’t exist in search.
Don’t take these warnings as a sign that Social will be a poorer-performing channel than Search; in fact, some clients may see better performance in search. Some brands are inherently more “social” than others. The only way to really find out for sure is to give it a try and give it some time.