Osborne Computer Corp famously committed suicide in 1983 by announcing a new product before it was ready to ship, thereby killing their cash cow (the previous product), and killing their cash flow, and killing themselves.
If you use Firefox 3.6, you should assume that, after August, there will be no more fixes, security or otherwise. If you want to get on board with their process, you'll need to start using Firefox 4. But wait a minute. Firefox 4 is dead too. You need to be using Firefox 5. And that will be dead in a few months, replaced by Firefox 6. And so on.
The problem for them, if they choose to view it as a problem, is that web browsers are done. Feature-complete. No one can think of anything to add that anyone wants, because there are no more features to add. Sadly, this happens to product categories. It happened with word processors twenty years ago. Spreadsheets, around the same time. Windows was done when XP shipped. Mac OS, yeah it's done too. I haven't used any of the new features. And by "new" I mean features introduced in the last eight years or so.
Software products have lifecycles. They reach a point where all they need is maintenence. Make sure it runs on new hardware. Fix security issues as they arise. Optimize. (Firefox could sure use that!) Teeny little tweaks that are almost unnoticable.
And where is the industry press? Why isn't TechCrunch all over this? Walt Mossberg? Are you guys all on summer vacation? Too busy to fend for the users? I don't really care if Mozilla wants to commit Osborne-like suicide, but I do care that millions of Firefox users who won't be upgrading to Firefox 4 anytime soon are going to be exposed to all kinds of nasty shit.
Another angle on this -- there must be a reason they're doing this. They must see something we don't. Like their numbers going down. Or the money drying up. Since they're open source and non-profit, shouldn't we be told what the issue is? Maybe there's another solution to the problem? Other than exposing the users.
Microsoft tried this too, btw. Left the users to deal with all kinds of nasty malware. Firefox may think their rise in popularity was due to something intrinsically nicer about their software. I don't think so. I think it was just that the virii that were attacking MSIE were not attacking Firefox.
Eddie Cantor: "It's nice to be important, but it's more important to be nice."
Update: I turned off comments for this post, as we're attracting people from Mozilla who want to tell us how great their new versions are. Thank you, but we can find your marketing materials elsewhere. As I said in one of the comments, this is a company that suffers less from an inability to communicate than an inability to listen.