Facebook is probably a bad acquisition channel for many SaaS businesses, especially after this week news on FB managers trashing their own ad targeting [1]. I do a little project where I analyze founder interviews, trying to discover which acquisition channels consistently work for founders [2] and around 90% of founders who mentioned FB as an acquisition channel working for them, also mentioned at least 2-3 more major channels (like AdWords, partnerships, SEO, etc.) [3]
[1] https://news.ycombinator.com/item?id=25529479
[2] https://www.firstpayingusers.com
[3] The only exception were e-commerce companies, they were much more likely to rely solely on FB vs. SaaS Companies