Where is the Marketplace for Part-time Work?

I know I've hit the subject of part-time tech work in the past.  But that was over a year and a half ago. In tech, everything moves at the speed of light.  As a result, you would expect that any question I would have had wayyyy back then would have been answered by now.

But... crickets.

I like to think there's no problem so big our development community can't figure a way out to solve it.  We're an extremely well-educated and curious bunch.  We have many entrepreneurs in our space. We have extremely diverse interested.

We've solved the problem of getting around town using spare capacity in cars (Uber), and solved the problem with staying somewhere else where there's spare capacity (AirBnB).  And there's a question here about the legality of those.

Why then is it so difficult to manage the excess capacity in the world of development?  I don't know of a single development team that doesn't have lower-priority tasks that need working on, while the full-time, primary employees and contractors do the heavy lifting.  Things like fixing the build server, updating installed dev tools with new versions, doing low-priority bug fixes that keep your site from looking really polished.

If I were a product team manager, I would love to have access to a part-time off-hours person that could pick up some of these small tasks and run with them independently and check them in, fully tested.

But it's weird.  I hear nothing on the part-time work front.  I do see the occasional developer wondering, as I do, about the possibility of moonlighting, but all I ever hear as answers is "Have you heard of oDesk, eLance, freelancer.com, etc.?"

I have heard of those, but serious articles warn against being either a client or a developer on one of those sites.  The warnings make it all sound as if it's a big scam.

Furthermore, this whole things seems like a good consulting model.  If you're a consulting company, why not have some extra folks on the bench to do short-term part-time staff aug at lower cost to your clients?  A way to scale up and down when you don't need a full FTE to get some things done? Consulting agencies, have you considered doing this?

I'm still focused on why we're able to solve spare car and space capacity with technology, but we can't do the same with technologists.  Is it that it's too hard to commoditize development work?  It's easy to specify a bedroom or a space in a car, but not a build system, so it's hard to figure a price for the spare capacity?

I often hear as an answer to the "I've got some time evenings and weekends, how can I leverage my skills to do a little work and get compensated?" question: "If you've got extra time, there's always open source frameworks begging for extra help getting features implemented.  Why not do that?" Sure, there's a lot of things I can do, technical and otherwise, if I consider volunteering an option. But when I'm looking to trade spare time for money, it seems that the well dries up.

What do you think?  Feel free to drop a line in the comments section below.