The filtration process is terrible; "everyone knows" that some people are more able than others, but it's very hard to quantify and very vulnerable to prejudice. And a particularly modern problem: if you give people a take-home test, they can outsource it across the globe.

I'm starting to think that the way out of this is guild-like structures where you qualify by producing a "masterwork" recognised as such by your peers. And then you don't have to prove yourself any more.

If the challenge is just allowed to be itself and not an employment filter, then it can be fun for all involved. I'm keeping an eye on Stockfighter myself, and I know people who do Project Euler for fun.