If you have access to the TV show "StarTrekDeepSpaceNine", study the culture of the species called "Ferengi". Their natural instincts revolve around mercantile and financial dealing. They pay money to visit someone in their house, or to have a conversation with a government official, or to worship their religion. Their officers pay their soldiers, per order. Their childhood games revolve around gambling and simulating stock markets.
They don't have wars. They sometimes have financial collapses; these rally them to the cause. Their only serious crime pattern is kleptomania.
An XP team works by pretending that it is payed per story. The team behaves as if the OnsiteCustomer took bids in "ideal days" or "complexity points" for each story, paid for an iteration, and at its end collected new program features that add value. They are expected to behave like Ferengi.
They do this because it's not pretending. The OSC invests real money in running a programming team, and expects a continuous return on investment. They should be able to cancel the project at any time, no love lost, and get back a working product expressing exactly the value of the money submitted into the system.
Strict code ownership would interfere with return on investment. Programmers without trust cannot efficiently fulfill their "contracts", which are the user stories they bid on.
In an economic model, programmers cannot simultaneously own source code, and own user stories. That would cause incredible friction. Hence, programmers own the UserStories, and the OnsiteCustomer owns the code.
--PhlIp
The Ferengi Rules of Extreme Acquisition:
Duplicating them probably violates Paramounts copyright or somesuch, but since someone else has already done this, I'll take advantage of the fact:
http://www.psiphi.org/DS9/rules.html
Here are some that I think are especially relevant to XP:
2. The best deal is the one that brings the most profit.
(Do the Stories with the most value first.)
3. Never spend more for an acquisition than you have to.
(DoTheSimplestThingThatCouldPossiblyWork.)
6. Never allow family to stand in the way of opportunity.
8. Small print leads to large risk.
(Communication. Don't leave things implied.)
9. Opportunity plus instinct equals profit.
13. Anything worth doing is worth doing for money.
(Anything worth doing has an acceptance test for it.)
18. A Ferengi without profit is no Ferengi at all.
(If your work isn't delivering business value, you might as well not be working at all.)
19. Satisfaction is not guaranteed.
(If the Customer isn't steering or driving, the Customer won't necessarily get what they want.)
21. Never place friendship before profit.
(RefactorMercilessly. Including code other people have written.)
23. Money can never replace dignity.
(Courage. Have it. Everything else will follow.)
27. There's nothing more dangerous than an honest businessman.
(There's nothing more productive than an honest team. They're likely to get the most done.)
31. Never make fun of a Ferengi's mother. (Insult something he cares about, instead.)
(Don't throw blame. Solve problems instead.)
44. Never confuse wisdom with luck.
(Never confuse code with no tests with code that's correct.)
51. Reward anyone who adds to your profits so they will continue to do so.
(You get what you measure: measure only success and reward the team when they deliver it.)
52. Never ask when you can take.
(It is easier to ask for forgiveness than permission.)
57. Good customers are as rare as latinum--treasure them.
(Applies without translation, except for the use of the word "latinum".)
58. There is no substitute for success.
("Play to win. Don't play not to lose." -- Beck.)
106. There is no honor in poverty.
(If you never get to ship your product, then your project doesn't count. Gear your process to ship regularly.)
109. Dignity and an empty sack is worth the sack.
(Similar to #106.)
162. Even in the worst of times, someone turns a profit.
(Even for the most doomed of projects, people like Wyatt Sutherland can turn them around. Learn to be like Wyatt.)
223. Beware the man who doesn't make time for oo-mox.
(SustainablePace. FortyHourWeek.)
?. It's better to live on one's feet than to die on one's knees.
(It's better to have Done The Right Thing and have the project go tits-up than to cave in and do things you think are wrong and have the project turn out the same way.)
-- DossyShiobara , from the XpMailingList