Here's a use case that motivated the idea: I live in a densely populated area where everyone around me has a car. Say I wake up to a flat tire. I'd much rather pay someone $20 to just fix it in 10 minutes than get the car towed or figure out how to do it myself. Imagine searching for "fix spare tire" on Facebook and receiving search results for five people that all live with-in two blocks. Choose a person, agree to pay with cash, they show up and fix the tire.
The service FB provides in this example has real value. If this service existed I'd actually use Facebook, take a good look at the ads and perhaps even pay a small monthly fee.
To use an over-used term I see this as "the Airbnb of everything else". It could be applied to simple plumbing tasks like fixing the toilet (which was a real pain-in-the-ass to figure out). It could even apply to borrowing vacuum cleaners! The point is there's under-utilized resources around people. Imagine FB helping people utilize these resources like Airbnb helps people utilize extra living space.