Under Bush Abbas was much less hardline in his demands. Since Obama came along and went on his arab goodwill tour and been taking arab side that changed Before his problems over welfare started every chance he got he would look to pick a fight with Israel and had very little criticizm of palestinians. Since then the arabs think that Obama is going to back any demands they make and so they are getting more and more hardline because they think they have an ally backing them. Neither Bibi or Livni could deliver Obama all the things he wants. The Israeli coalition system & the power of the settlement movement makes it impossible. Even the left can't put together a coalition will agree to freeze all settlement building or building in east Jerusalem. The Gaza pullout alone was a hard sell & thats the area the Israeli public care about least This is a no win situation because neither side can back down and Obama doesn't understand this conflict he just likes to pretend he does for image.
Five people killed in car crash near Hebron (Haaretz)
from the article: Abbas refusal to meet Netanyahu could scuttle tripartite talk plan