Unless you've been hiding under a rock, you'll no doubt have heard Apple's recent announcements:
Is it me, or do these announcements sound like Apple tightening those lock-in strings previously associated with Microsoft? It smacks of "if we can't control the code from start to finish, you can't have it". We already know interpreted languages like Python, Ruby, Perl, PHP, Flash and Java are not allowed on the iPhone or iPad under Apple's Ts & Cs, but how long before these are "banned" from OS X too? How long before the Mac App Store is the ONLY way to install software on your Mac (without hacking it)?
I know this sounds a bit far-fetched at the moment, but I really wouldn't be surprised if this comes to fruition. Apple has seen great success with the iPhone, iPod and iPad with their interaction with the app store and they are now bringing this to the desktop environment. Apple has very successfully used their "oooo" factor to change the world into "data consumers" under their terms and bringing this to the desktop environment will be very very lucrative indeed, especially if Apple can control the entire stack. Once they've got everyone hooked, it won't be too hard for them to shut the door and then you'll be locked in, just like on Windows :-).
Recent reports say desktop Linux is dead, maybe not.