Use case for hypothetical website, baddrivers.org:
You're walking down the street, and some asshole honks their horn just as they pass. Or your'e riding a bike, and they drive you into the parking lane. You're pissed. But what are you gonna do?
If you get their license plate number, you could go to baddrivers.org, and for a nominal fee (say, $5.00), anonymously assign demerits to the bad driver. Inasurance companies might then use the data to assign insurance rates. Bad drivers could get their records expunged by paying penance. Penance fees would go to pay for driver's education courses, MSF courses, etc. Since you have to pay to assign demerits, you would not be able to post too many merely malicious demerits (unless you're rich).
Ancap, Inc. -- Ancap defense agencies have to date, been largely theoretical. How would you start one? It seems to me that the biggest problem such an agency would face would be protecting its clients from the U.S. government. For example, what could a defense agency do to protect me against the U.S. government if I wanted to, say, smoke pot?
It seems to me, you don't want to compete directly at first - the U.S. government would squash you like a bug. You want to grow big and strong in areas that could be repurposed as part of defense agency, but would not be noticed by the U.S. government until it was too late.
Some fields that would have direct relevance:
* Cruise ships
* Arms manufacturing
* Commercial security guards
* Radio, TV stations
* Satellite communications
* Ship building
* Real estate
What would be a low capital business to start? Perhaps pre-paid legal insurance? For a monthly fee, you get the right to a certain amount of legal representation. You'd agree that disagreements between other clients would be settled via arbitration.