"Any ideas on what these people have in common? All House members are up for re-election, so that's not it."

Well according to Dennis Prager, the most liberal dems voted against it.
I don't know the names well enough to say, but my rep [a dem] voted for it, and she is fairly conservative- or least, certainly not a far lefty.
Prager was for passing it, and said that reps should have at least considered again their vote, considering how many liberal dems voted against it.

But I would say, it was *mostly* a matter of looking at poll results of the American public and that American public are against it. Or as instapundit said:

"I keep hearing that opposition to the bill from constituents was overwhelming for members of Congress of both parties, with the House switchboard and website overloaded. And certainly the bailout polled badly. So, whether it was a good idea or not, the rejection would seem to meet with the voters's approval. Of course, the politicians know that if it turns out badly, those same voters will still blame them . . . ."
http://pajamasmedia.com/instapundit/

I would say it's mostly a matter of poor dem leadership- not that Senate leadership helped in the matter- and the nearest to the elections.