I guess the problem with this analogy is that it fails to capture the essential nature of Facebook: that its base product ("hamburgers") has a network effect, and the new product ("candy") doesn't.

If Facebook is a social network for seeing my friends, then there's nowhere else for me to go. They're on Facebook and it's unlikely they're all going to join some new network at the same time.

If Facebook is a high engagement content farm designed to shove random engagement-bait in my face, then it's just competing with Reddit, Digg, Twitter, 4chan, TikTok. Folks can get addicted to this in the short term; but they can also get bored and move on to another app. Based on conversations with all the IRL human beings I know, this is what they've all done. (The actual question I have is: who is still heavily using the site? Very old people?)