> It's not really about motivation. Difficulty of terminating employment can make employees a real liability when you're small if they turn out to be a bad fit.

Given significantly smaller salaries and the typical 3-6 months probationary period before going full time, I don't think this is much of a risk. If someone turns out to be a 'bad' fit 6 months in, the employee isn't the only thing in need of looking into.