I've been to an OpenBSD hackathon (which has been doing them since 1999) and I think those and the Haskell hackathons differ from many of these new events that people are calling hackathons.
For OpenBSD, the developers are all working as a team on a central project, but usually have sub-projects or tasks related to OpenBSD that they've been working on independently prior to the event. They bring their code to work on or debug, they meet new developers that are normally scattered around the world, test code on different machines, discuss new projects, and socialize (which usually brings out more ideas). Most of the time, those ideas aren't finished at the end of the event, but they've been given some direction and help or have been inspired to start on something new.
The hackathons that Winer is writing about are basically just competitions to see who can throw something together in 24 hours or however long the event is. The ones I've seen put on by Facebook and Twilio seem like nothing more than marketing for their own products, and the developers get some marketing for themselves by winning the competitions.
I've never been to an OpenBSD hackathon, but I've heard good things about them from others. They get a lot done on ports and various projects (PF, OpenSSH, etc) during the hackathons. It seems to be a big part of their culture.
For OpenBSD, the developers are all working as a team on a central project, but usually have sub-projects or tasks related to OpenBSD that they've been working on independently prior to the event. They bring their code to work on or debug, they meet new developers that are normally scattered around the world, test code on different machines, discuss new projects, and socialize (which usually brings out more ideas). Most of the time, those ideas aren't finished at the end of the event, but they've been given some direction and help or have been inspired to start on something new.
The hackathons that Winer is writing about are basically just competitions to see who can throw something together in 24 hours or however long the event is. The ones I've seen put on by Facebook and Twilio seem like nothing more than marketing for their own products, and the developers get some marketing for themselves by winning the competitions.