The old school strategy was to hire a student as a summer intern and if it's recognized as a good fit by the end of the summer then ask them to apply after graduating. The second step (for people past that stage) is to trust but verify the work experience they list on their resumes. The difficulty these days is that companies want candidates to be a perfect match for the company's current tech stack.
I expect a lot of that is due to the referral being familiar with an already ensconced employee, as well as the referrer being incentivized to ensure the referral's success.
I've heard that MS took a different path (than previously) for the Windows 8 Metro design and wonder if a big source of the initial UI issues was a result of shoehorning the new design into the existing Windows UI.
The main point of the screening is to have a highly structured question and answer session that is recorded for posterity, and which can/will be referenced at the next screening 'n' number of years later.
One could even argue that the polygraph benefits the person being screened, as it provides some additional motivation for them to take it seriously.