Well, time for corrections:
Yesterday, I posted a little article on a finding I did in the morning: QuickTime Player X played .flv files. I just confirmed it was wrong. This is the background of the story:
I had installed Snow Leopard (WWDC release) last Friday, rather quickly as I was in a hurry. When I came back yesterday, I found a "Previous System Folder", which I promptly deleted. Thus I assumed I had done a clean install of Snow Leopard. Then I started digging around in Snow Leopard, and much to my surprise, I found it played .flv files. Since I had not seen that fact reported anywhere, and considered it of significant interest to many Mac users, I emailed John Gruber (author of Daring Fireball) to let him know.
In the evening, I had received quite a few comments to the previous article in the blog, suggesting I had Perian installed (providing the ability to play .flv files in QuickTime Player), but that QuickTime Player X does not play natively .flv files. Since I had read them at home, I couldn't check the comments until this morning. And this is what I did when arriving at work. And as suggested by many comments, effectively, I had Perian installed, enabling the .flv playback in QuickTime. Which means I had not done a clean install (but then, I can't understand where the "Previous System Folder" came from).
So, to summarize:
1. NO, QuickTime Player X DOES NOT support natively the playback of .flv video files.
2. I apologize to all readers who were confused by my previous article on this topic. I posted it honestly convinced it was true and of interest to other people. So I am sorry for the confusion. Next time I find something this exciting, I will double check before making any announcement, instead of letting my excitation take over.
3. I am really surprised by the huge noise made by this little comment from me. The take home message (for Apple) is that there is a very strong interest in the community of Mac users to see such native support for .flv playback in OS X and QuickTime. And if I was responsible of the development of OS X, I would hurry up to include such support in Snow Leopard before its final release after the summer.