Releasing a product that is crippled to increase the number of people coming to you for support is extremely unethical, and likely won't get you significantly more business anyway (re Anderson: they'll probably just find another plugin).
You can charge for the product and/or for the support, but both the product and support should be good quality. That doesn't mean you have to go out of your way to make absolutely certain nobody will ever need support, but you shouldn't cripple the product. If one were to cripple their product so that they could generate more revenue from support, what's stopping them from providing sub-par support that requires the customer to pay for even more support?
You always win out by providing a good product and good support. There will always be people who, as Anderson says, can't even find the wp-content directory, but you shouldn't have experts coming to you with questions about the basic functionality of your theme, plugin, etc.
Look at Windows, OS X, etc... your average to expert computer user can generally get along just fine with little or no support, yet there are still those who need (paid) assistance with even the most basic tasks. However, as a technical user, if I weren't able to use an operating system I paid for, I wouldn't pay for support, I would use a better operating system.
I think JellyBeen says it best, "the product would inspire additional paid services, not demand them with inadequacies".
For what shall it profit a man, if he shall gain the whole world, and lose his own soul?