Can people at least get their terminology right for once here? That isn't what proprietary means, and conflating "patented" with "proprietary" simply serves to confuse people.

Many free software programs are covered by at least some patents--most, I would say, simply given the size of the patent minefield--and I wouldn't call them "proprietary". It seems to me that "proprietary" has basically become an insult to be applied towards anything "less free" than what one wants to advocate.

A proprietary format has no standard you can freely read and implement. At best it requires signing an NDA and/or paying tens of thousands of dollars to look at--at worst it doesn't even exist, with the "standard" being "whatever the official implementation does" (see Microsoft Word for a great example of this). There are tons of these in video: RealVideo, for example, along with all of Microsoft's video formats before they finally opened up with VC-1. Others include On2's video formats (e.g. VP6), Sorenson's (SVQ1, SVQ3), and many others.

One of the biggest dangers of this conflation is the understatement of the dangers that proprietary formats can cause. There has never, ever been a lawsuit over an open source implementation of a "patented-but-standardized" file format--as far as I know, the common interpretation seems to be that the sellers and distributors of an application are responsible for any royalties, placing no restrictions whatsoever on the developers. See LAME, for example.

But proprietary formats are different. The law is very vague and conflicting on whether or not it is legal to even reverse-engineer such formats (it varies between countries as well). Doing so almost always requires access to the disassembled binary of the original application, which violates the EULA and potentially the DMCA. Developers can be hit with legal threats merely for releasing source code, as we saw with RTMPdump.

Of course, proprietary formats tend to be patented as well, resulting in a "worst of both worlds" situation.

Don't mix up the terminology, lest people be convinced that RealVideo or another proprietary solution is no more evil than a internationally standardized, albeit patented, option. The greatest accomplishment in internet video in the past 10 years has been moving away from that horrendous mix of Quicktime, Windows Media, and Real that was used on almost every site on the internet. Even if it means we've been stuck with Flash for playback until recently, it's better than that ridiculous mix of proprietary garbage.

http://news.ycombinator.com/item?id=1074237 has a great example of what happens when proprietary and patented are conflated: a piece of proprietary crap can be promoted in place of a free software solution.