Sometimes a trend seemingly defies logic to such a degree that, well, all I can do is blog about it here.

The news: Sales of blank audio tapes are on the rise.

The advent of the compact disc put the first nail in the coffin of the audio cassette over 30 years ago, and nothing has stopped the move away from the last major analog format ever since. The growth of online music and the iPod, which wholly killed off the portable tape player market years ago, seemed to be the final straw for the humble cassette.

But that hasn't happened. In fact, sales of blank tapes are curiously heading up instead of down of late.

To be sure, tape sales fell off a cliff throughout the '90s and '00s, from three billion in 1988 to five million by 2007. But now they're at a point where they're rebounding -- however slightly -- with TDK alone on track to sell at least three million tapes in 2009.

Why the resilience in this market? To put it simply, installed base is a heck of a thing: Once people have a gadget, they tend to stick with it until it's dead. (It's the same reason why HD DVD movies and VHS tapes keep selling -- that and the rock-bottom prices.)

Of course, cassettes have an enormous installed base, and the fact that many cars were including tape decks long after the in-home market had migrated to disc has kept the format alive. It's a lot easier (and cheaper) to drop a CD player into your apartment than your car, and many people seem to have chosen to simply live with what they have until they replace their vehicle (which, given the slump in auto sales, may not be anytime in the near future). Auto tape decks also have an enormous talent for resisting being stolen.

Tapes also have the great advantage of being perhaps the simplest recording format in history. Making a mix tape doesn't require a computer or anything beyond a basic understanding of how to connect a few cables and pushing the red button. Burning CDs means a PC has to be involved -- simple for the readers of this column, to be sure, but far beyond the ken of millions.

There are also plenty of original recordings still being put to good-old analog tape: As Sky.com notes, "lawyers don't trust digital technology for interviews," and tape is still commonly used for depositions.

Same usually goes for reporters, too: I've got half a dozen digital recorders lying around, but when I need to record an interview and know I'll need to hold on to it for months... my good old microcassette recorder is always within reach.