Tax arbitrage. More details here:

I also made a little comic book outlining how you can use loan shark for tax arbitrage, and I go over the comic book in the video at timestamp 10:07: http://tinyurl.com/ye2avw7j

I expect most plebs would rather lend than borrow. Borrowing makes sense if you have a lot of old bitcoins and are currently living on them, spending them day to day and incurring big tax penalties.