- While it's true that she hasn't put out a Shermanesque refusal, she's been a lot more adamant than most "just playing hard to get" politicians who actually plan to run. I don't think she'll acquiesce to the "draft" efforts, put together a campaign and go for it.
- The Democrats haven't run an even slightly-to-the-left-of-center presidential candidate since at least as far back as 1988 (probably 1972, actually) and I doubt they're going to start now. Bill Clinton mopped the floor with Jerry Brown in 1992 and the Democratic Party's centrist wing has dominated the nomination process ever since by hook or crook. Al Gore whipped Bill Bradley in 2000, John Kerry aced out Howard Dean in 2004 and no candidate of an even slightly leftist bent made a significant showing in 2008. Warren knows this, and therefore she knows that even if she wanted to run, she would end up doing so as a flag-shower and sacrificial lamb, not as a likely nominee. And why do that when there are other things to do that advance her agenda more?
I also doubt that Warren will be on the short list for veep. If Hillary Clinton receives the nomination, she'll probably choose a male running mate on the supposition that even if America is ready for a woman in one of the two top slots, it's not yet ready for a woman in both at the same time.
I won't be surprised if Warren ends up with a cabinet position, though. Assuming the Democratic nominee wins the White House, that is. At the moment, that looks like a safe assumption, but two years is forever in politics.