Definition: Open Source Zealot - (n). One who supports open-source software (OSS) religiously. Will refuse to use software unless it is open-source. Has many insults and assumptions about closed-source software.
Personally, I think that these guys are one of the things that hold Ubuntu back. They demand that everything be open-source on Linux, and then wonder why many hardware manufacturers do not make drivers for it. And when the manufacturers actually do make drivers for it, the OSZs call it "buggy closed-source software." Last I checked, the open-source equivalents are generally buggier, or less functional. Compare ATIs closed-source drivers to the open-source ones. Proprietary: probably won't support your hardware, but very functional when it does. Open-source: 2D graphics only, no 3D hardware support (so effectively the same).
The Ubuntu developers are aware that the proprietary drivers are better, but they can't have them enabled by default or they will be demonized by the open-source zealots. Instead, they have to label them as "Restricted" and specifically ask the user if they want to install them. If average Joe uses Ubuntu (it is important to note that Joe does not know anything about open-source, nor does he care) and sees this little pop-up that says "Restricted drivers..." he will think it's a bad thing like a virus and panic. "This whole new operating system is already scary enough and now it's telling me that I have restrictions!" Gobuntu should be the only one that differentiates between closed and open source, the other versions of Ubuntu should by default have closed-source enabled and if the open-source zealots want to disable it, they can by all means do it.
The one thing that open-source zealots really do not understand is that the computer market (probably more than most markets) is governed by economics. Economics dictates that firms are rational, profit-maximizing firms (with exceptions of course). The majority of firms are in the business to make money. They can't make money off of open-source software, so why would they make their software open-source? The costs of making the software open-source by far outweighs they cost of making it closed-source and charging for it (the cost here is that they have to take flak from open-source zealots). Also, the money that comes in from sales can be used to pay lots programmers to work full-time and even overtime. Large teams of programmers working 40+ hours a week and not having to work elsewhere to earn a living can get a lot more done than one or two hobbyists programming in their spare time on open-source stuff. In the days when Richard Stallman first started the Free Software Foundation, most pieces of software could be made by under five people in six months to two years. How many man hours went into designing Visual Studio, or Oblivion? These could not have been done in a reasonable amount of time under an open-source license. On a side note, one should observe that Vista took 5 years to come out not because the programmers were not productive, but due to the fact that Microsoft has the desktop operating system market in a choke hold and has no pressure to release the software on time.