It doesn't concern me terribly.  It's not uncommon for significant segments of a party base to say they won't vote for this or that person.  The losing candidate's supporters will bitch for a while (as we saw at dKos when Edwards dropped out), but eventually they come around.  It's also the case that Democrats generally carry a smaller portion of Democrats than Republicans carry of Republicans.  It evens out because there are a lot more Democrats (36% of the country) than Republicans (27%).

Queen Hillary the Survivor, like St John the Maverick, is a media creation.  She's never had a real opponent prior to Obama.  (She won her Senate seat by using her husband's presidency to push out a congresswoman who was, up to that point, the presumptive nominee, and then coasted to victory in the general because Rudy! was diagnosed with cancer and dropped out.)  She survives because of the fact that the press wants to keep the Clinton Soap Opera going.  If the Windsors and the Dukes of Hazard could be smashed together, the result would be the Clintons.

I think you're giving Clinton far too much credit here as a human being.  The unfortunate truth, or at least so I believe we'll find, is that she'll keep going until forced to get out.  (Rest assured that if she were getting ready to call it a day, she wouldn't be having her donors write obnoxious letters to Nancy Pelosi over Pelosi's comments, or threatening Howard Dean over Florida and Michigan.)  If that destroys Obama in November, it just means she's gets to try again in 2012.  If she were going to accept defeat graciously, -- I, frankly, think we're long past the point at which she can -- she would've dropped out after Texas, at the latest (going out on a high note).

Put simply, you're assuming the Clintons will observe the niceties.  After all, Edwards did.  Richardson, Biden and Dodd did.  Obama, to this point, has.  Candidates always do.  Clinton, however, has not, and all the press talk of "Well, if she gets the shit kicked out of her in this or that state, she has to drop out, or the math doesn't work" sounds great, but we ultimately find it proven silly when she winds up, you know, getting the shit kicked out of her in this or that state.  (The only thing that winds up changing is that whatever state the press referenced is branded "insignificant" for a variety of reasons -- too many blacks, too much money, not enough Mexicans, too many young people, undemocratic caucuses, sexism, affirmative action, Republican conspiracies -- by the Clintons and Mark Penn.)

I'll happily swallow my words if I'm wrong, but remember who told this to you when Denver comes and Clinton is clawing her way there from Puerto Rico: The Clintons are not honorable people, and Lady Macbeth (as TBG likes to call her) will stay until her candidacy is killed by the superdelegates.

Be nice to America. Or we'll bring democracy to your country.