Why the sudden popularity of 12 inch arms

Shane, the major differences I find between 12" and it's 9" counterpart is the way the music is presented. The shorter arm would have better detail, speed, transparency and more of the hi-fi thing (if that's what you're looking for) while the longer arm presents music in a more effortles, relaxed way with less highlighting.

They are just different and hard to compare...just like apples and oranges.

And, after upgrading to a 12" arm, the next step is linear tracking.

The advantage of 12 inch arms is nothing new, nor are their shortcomings.

And, after upgrading to a 12" arm, the next step is linear tracking

True

On paper a 12" arm is superior, but when it comes to manufacturing one it is not so easy. I think the combination of technical advancements, lowered manufacturing cost (or conversely the reduced aversion to a high cost arm), and the need to expand the product line (as others have said) are driving this. We are a fickle bunch so the desire to have the latest and greatest has a lot to do with it to.