Enlarge (credit: Andrew Harrer/Bloomberg via Getty Images) I’m a regular Venmo user. I used the service a month ago to receive $30 from my sister-in-law. I used it again two weeks ago to reimburse my brother after we threw our father a surprise birthday party. It’s a perfectly useful service. But unlike most Venmo users, I have my transactions set to "private"—and I've never understood why the default setting was "public." Why would I want the world, even my Internet friends, to know when I settle bar bills? I know of no mainstream payment system that makes its transactions public.