A lot of open source projects are just a single person doing it in their spare time. Throwing more bodies at the problem is exactly what is useful there. If you're developing on your own in your spare time it can hardly be called disorganisation.
Exactly useful to whom? The tossing of warm bodies seems a rather suboptimal way to build teams, much less communities; perhaps because being tossed provides so little utility to the warm body. Building sustainable teams and communities around an open source project is always going to be hard work and a low barrier policy on HN that encourages requests for help doesn't change that.
Useful to anyone even remotely involved in the process. The random helping hand gets that warm fuzzy feeling of helping, and nerd credz. I've done this before, it really is a motivator. The sole maintainer gets assisted with their roadblock. All users/watchers of the project get to rejoice because the project has progressed.
I do not see why you focus so much on team building when that is completely unrelated to what is being discussed. Not all open source projects are big enough to warrant any kind of team. They're literally just someone's side project, which may or may not be useful to other people.
I don't really think either of us can reliably substantiate predictions of how it would pan out but, considering that in this very submission, help was asked for, received and open-sourced at that behest at no cost to anyone (how awesome is that?), the idea stands validated at 1:0. :)
A few years ago, around the US Thanksgiving holiday, there was an "Offer HN:..." thread. Over the next few weeks, there were a number of genuine offers from very capable people. It was really awesome
But eventually, it became what any cynic would expect: a mechanism for "We will build your iOS app for $2500" offers and today it's dead. This isn't a 1.0 release. It's a 0.1 alpha. Nobody has written the 400 lines of good expert code requested. The existing C code that has been offered may or may not blow up under the OP's load or not meet their exact needs. No one is claiming it is bet-your-business ready. The fundamental open-source project problems of maintenance and further development are not solved or even addressed.
More importantly, it hasn't been demonstrated that this mechanism works for getting people to substantially support the project with more than the goodwill of contributing existing code developed for another purpose. Don't misunderstand me, that's a great thing. Which is why a once a month format is a reasonable starting point.
