The Hill asked all 97 Senators not running for President if they would accept an offer for Vice-President... I thought it was worth posting Jim Webb's response:
Sen. Jim Webb (D-Va.)
"I'm not really interested. That's all I want to say."
In reality- I don't think anyone who was offered the Vice-Presidency would realistically turn it down... including Jim Webb (who would make the perfect addition to an Obama ticket).
If you're interested- John Warner would also turn down such a bid :)
Sen. John Warner (R-Va.)
"No, I'm not getting into that. I'm happily in the twilight of my retirement."
2) While he is not interested, he would not absolutely rule it out. It would depend upon the shape of the office, the expectations for him during the campaign