"Not so much" at the end of a sentence

I've occasionally seen "not so much" used at the end of a sentence. For example, Jeff Atwood saying

Some community feedback is useful. Others, not so much.

Doing a symbolhound search for "not so much.", I came across entries such as

1. First one good. Second one not so much.
2. That worked fine on the development systems, but on a production system, not so much.
3. iScroll would be what you need. And unlike jQuery mobile, iScroll works on various devices and on the desktop. jQuery mobile, not so much.
4. Again, Safari and Firefox show this, Chrome not so much.
5. The lambda I can see the point of. Sending 'fn' to almost-but-not-quite 'f', not so much.

I assume that placing it at the end of a sentence is non-standard English. Is it derived from some quotation or meme?

Urban Dictionary has some entries for it, but they don't describe how the phrase originated, or even use coherent sentences.

(I'm aware of what not so much means when it's used in a more standard manner)

The phrase is meant to be dismissive and is a somewhat current catch-phrase that has been used comedically by some television celebraties in the US. While looking for the source of this expression (one of which cited the origin as the "Brady Bunch", a highly popular and iconic sit-com from the 1970's), I came across this excellent article by Daniel Weiss from the Columbia News Service - the gist of which is that unlike other catch-phrases that have a brief moment in the spotlight such as "Been there, done that" and "yada-yada-yada", "not so much" has a certain style of being dismissive without being downright rude. It was compared to fashion in that one can put it on (i.e., use the phrase) to come across as humorous/dismissive.