Please don't call things "Uber for X", it's a completely meaningless sentence most of the time. When you say "Uber for banking" to me I have to idea what you mean.
If you think for a minute that's pretty hilarious. Sharing economy indeed.
Well you see, when you're carrying a lot of cash on your person, then you put your location on a website, so anybody looking for someone with a lot of cash can find you and...
...hmm.
When I was in Nicaragua for awhile it was kind of known you don't fuck with the cash dealers. From my experience, especially in these lower-income countries where these services are targeted, you're either getting protection or you're providing it; if neither, you'll quickly find yourself needing one of the former.
I'm not sure how this would change with a Silicon Valley style startup, but given Uber drivers don't know each other or have any "loyalties" for lack of a better word, I'm inclined to think you'd be right. However, I can quickly seeing this leading to the "dealers" on this system organizing into a group for self protection. Or a gang, cartel, militia, party, or advocate group, whatever you want to call it. Dudes you don't want to fuck with. And that doesn't sound conducive to a banking revolution, although maybe in the sense that payments are a social system at their core could make this feasible.
Do you know how many Uber drivers have been charged criminally?
Just think of controversial or antiquated laws and build Uber on top to facilitate the transaction. Uber of drug dealing...Uber of prostitution...unlike Uber of banking I bet you know exactly what those mean.