People will be hacking their vehicles, right? They can program any behavior they want, right? NYC's off-street parking rates can easily exceed $20/hour. It is CHEAPER to tell your car to drive around aimlessly waiting for you than for it to park. Sure, traffic is miserable. But you aren't in it, so it's okay.
Find 15-minute loading zones. Park there for 15 minutes. Move to another one (your spot immediately taken by another empty vehicle). Repeat.
Park next to fire hydrants at no cost. Use the same visual scanners you use to navigate to detect approaching police and parking enforcement, and if one is detected, drive away.
There are limitless opportunities for self-serving behavior that ends up being hugely anti-social when any significant portion of the population does it. Basically there are three choices:
1. self-driving cars are locked down as all hell, The Man controls them all (proactive enforcement)
2. all the bad stuff is fined out the wazoo - Arab sheiks and Steve Jobs just pay the tickets, but no one else does - (reactive enforcement)
3. self-driving cars create a miserable traffic situation for everyone, in a massive tragedy of the commons problem (no enforcement)