We rely on subs/strategic partners everyday. We use a sub contract form our lawyer provided that lays out all the ground rules (insurance, payments, non solicit etc...). Like a previous poster said, a lot of our subs are former employees.
On a different but related note, read an article recently about strategy and strategic vision in business. Back in the 1960's, Nike's laser focused vision was "crush Adidas". They were the big boy on the block at the time and Nike wanted to take them down. I think having a David vs Goliath mentality can be a good motivator - as long as it doesn't spill over into bad mouthing the competition to potential customers.
At the end of the day, no one owns a customer. You have to work hard everyday to earn someone's business. If a customer leaves your company for another - better look in the mirror.