Mr. Groo is correct.
Also, all of this "Long Tail" business dances around the fact that it is still a very dicey proposition to R&D new product aimed at the "Long Tail buyer" or whatever you want to call them, because it's a whole lot harder to recover fixed costs that way.
Almost by definition, much of that stuff in the "long tail" is, in a word, old. Specifically, it's old and already paid for. Same thing with those catalogs like "Products You've Never Heard Of But Can't Live Without"--it's not like GSK scientists are working through the night inventing those things, they're mostly old, the plastic molds or tool dies or whatever to make those things were built and paid for long, long ago. It's okay that there's only marginal demand because they only incur marginal costs to produce and sell.
This all works particularly well for mail order/Internet retailers, particularly when it's a digital product and inventory costs are virtually nil, because the investment has already been put into the product. GameTap can do well enough selling a library of old games at an attractive monthly rate because the rightsholders of those games aren't looking to make back the whole production cost, just to pad their revenues. Developing a new game for GameTap etc. isn't unheard of (Sam and Max) but it's still not a slam dunk. Guys like Thomas and me implicitly believe that there is some hope for us to sneak into that kind of success as well... but we can't plead ignorance if it turns out we are wrong.
So the way that it has "changed marketing," if at all, is by creating more attention to old stuff that's been bought and paid for. Little different than your standard Foreigner's Greatest Hits album, except now it's "Greatest Hits of NES RPGs" or whatever, and every TV show you've ever heard of on DVD. (Except Herman's Head, the bastards.)