Where I am employed we are actively hiring. In late 2012, three of us started a small experimental projected which became a hit with our customers. As more feature requests came rolling in we realized that we need a bigger team to work on the project. We have been hiring since the start of 2014. We now have a team of about 15 engineers, but we still have few more open positions.
From our experience, resumes usually are not a good predictor of anything we care for. The only useful thing it tells us is what firms the candidate has worked at, and what those groups were doing while the candidate was there.
When a candidate comes onsite we spend significant time showing a demo of our product, what our groups ambitions are, discussions to understand what the candidates career goals are etc. We also have the standard white-board interviews, often attempting to design a small feature on our product. This takes significant effort on our part. Before investing this time, we will prefer to see some code from the candidate.
The candidate is offered an option to show us (1) some code they wrote which is out in the public domain, OR (2) some code from their employer (if their employment terms allow it) OR (3) solution to a small coding question we provide. Our coding question takes about 4-5 hours of the candidates time.
This process has worked very well for us. We have been able to screen our candidates with very impressive resumes who wrote horrible code. We have also found many great candidates (some who are my colleagues now!) with ordinary looking resumes.
I hope I have tried to explain our thought process behind asking candidates for some code.
Another thing to keep in mind is that for a lot of people who are already employed, permission must be obtained from current employer before contributing to open source (and more and more companies are actively enforcing that unfortunately).
I am always puzzled about contract clauses that try to limit what an employee can do in their free time. I understand that some people may be in a bad situation and have no choice but to put up with it. But if we're really in a seller's market, as everyone says, how can this kind of thing become a tendency?
This is further reinforced by various employer-specific clauses in the hiring contract / code of conduct.
Its screwed up but its the world we live in.
Any employer who puts that clause in their contract and whinges about not being able to find good developers has only themselves to blame.
Won't hold my breath.
I'm sick to the back teeth of most of these mini coding projects, though. They're too often sent by companies who aren't even sure they want to hire at all or wouldn't hire you anyway for some unrelated reason (age, race, etc.). The projects are always boring and almost never suitable for a portfolio.
It's also too easy to hit the 'send email' button and too easy to ignore the responses. Unless there is some cost for the company sending you the mini-project, a lot are going to waste your time.
For this reason, I actually prefer interviews. They're going to at least do a cursory examination and reject you outright before wasting an hour of their own time.