"Can we FaceTime?" If I had a nickel for every time someone has asked me that, I'd almost be able to afford a new Android tablet. And yet, even then, I still would not be able to FaceTime, because I don't have an iPhone, iPad or i* anything else. This fact has had me wondering: Why does anyone use Apple's (AAPL) FaceTime, given that it is a redundant, proprietary VoIP application?

The fact that so many people want to connect with me over FaceTime leads me to believe that one of the following two things must be true:

I don't know which of these possibilities is the case. And it doesn't actually matter, since, either way, I still cannot explain why FaceTime has become so popular, given that other VoIP apps—most notably Skype, though there are others, like Google Hangouts—have been freely accessible and compatible with a variety of different operating systems and hardware platforms, for more than a decade.

In contrast, FaceTime has been around for only about five years, and—although the app itself is technically free—you need to buy Apple hardware to use it.

This isn't to say I'm in love with Skype. It has its issues. For one, as a Linux user, I wish Skype were open source. (It seems unlikely that this will ever be the case, as Skype is now owned by Microsoft [MSFT].) I also wish the Linux version of Skype did not tend to lag behind the Windows one feature-wise.

That said, Skype works perfectly well on Linux, and virtually every other operating system, for both voice and video chatting. I am therefore perplexed by the fascination with FaceTime, which brings nothing novel to the table for Apple users, and which makes life more difficult for non-Apple users who can't connect with their iPhone-touting friends over FaceTime.

The Late, Great Cross-Platform App

But that's not what makes this a really big deal. What's truly interesting is how FaceTime exemplifies the way companies such as Apple have managed to make cross-platform interoperability—one of the core components of the personal-computing revolution of the 1980s and 1990s—increasingly a thing of the past. More than anything else, the cloud was supposed to let everyone run the same apps, share files seamlessly and so on, regardless of which particular operating system and hardware platform he or she used. Yet the exact opposite is happening as proprietary apps such as FaceTime have exploded in popularity.

That's perhaps the greatest irony of the IT world today. It's also a sad one.