"At the top of the corporate world, pay-for-performance takes forms such as profit sharing and stock options. The rationale behind all these motivational incentives is that 'money talks'. People want money, so if you structure the situation correctly you can get them to do what you want.
The results of [my] studies cast further doubt on the efficacy of these pay-for-performance practices, however. Of course, these practices can motivate people, but in the process, they will likely encourage shortcuts and undermine intrinsic motivation. They will draw people's attention away from the job itself, towards the rewards it can yield, and that without doubt will result in less effective, less creative problem solving."
From Why We Do What We Do by Edward Deci (who seems to be the grand-daddy of much motivation research).