Have you used Venmo before? Either way, if you connect your contacts (not sure if it's just FB or overall contacts too), I have a hard time believing you won't see at least one semi-active person you know using it. To be sure, not saying you should connect your contact info to Venmo. It is a privacy matter after all.

Even my dad who has virtually no real friends outside the husbands of my mom's friends, had multiple contacts using Venmo when I got him to use the app so we would have an easier time paying for stuff between us.

I don't know a lot of people, but my Venmo activity feed of friends has at least a dozen transactions a week. I have ~300 FB friends and about half that in Venmo "friends".