Earlier quoted context omitted.
Excellent question. Anything that doesn't have a natural monopoly. I can say with certainty that the following should be socialized or delivered in non-profit ways: * Water * Sewer * Power * Internet * Healthcare * Fire * Police * Roads * Education (added per /u/CodeMage) Feel free to chime in if you can add anything I forgot.
Education, Police, Fire, Healthcare do not have natural monopolies. Still a good list to have around so we can argue about where the line should be drawn. Kudos!
Education is tricky, and honestly, I don't know any better than the next guy how to solve the issue. What's important to one parent may not be important to another. Second language? Art? Music? Sports? Recess? Lectures? History? Religion? Critical thinking? What outcomes are important? Good test scores? Writing?