Do you own the software that runs your Tesla?

When Tesla announced recently that it would make "full self-driving capability" available on new S and X models for a mere $3,000 extra, optimists hailed the development as a watershed moment for consumer technology. But embedded in the press release was a little-noted catch: While customers may use the self-driving feature to pick up friends or family members, "doing so for revenue purposes will only be permissible on the Tesla Network, details of which will be released next year." If you want to earn some extra money -- perhaps to help pay off your robot car's $75,000 price tag -- by selling rides to strangers, you won't be allowed to use Uber or Lyft. On its face, this demand may seem ridiculous. For over a century, buying a car meant that as soon as you left the lot, you could drive it wherever and however you liked as long as you obeyed traffic laws.