So many Israeli settlements, in particular Ma'ale Adumim, are built largely on private Palestinian land. So that accounts for about 40 percent of their land area. So?
This information was leaked from inside the Civil Administration (the Israeli government body responsible for the occupied territories). The Yesha Council, as usual, responded by lying (see the Ha'aretz article cited below) and the government responded in its usual way--by essentially admitting that this was true and saying nothing. For example: "Miri Eisin, a spokesperson for Prime Minister Ehud Olmert, said that Israeli officials would have to see the data and the maps and added that ownership is complicated and delicate." Of course they need to see the data and the maps, it's not as though they've had access to them before! Inevitably they will have to conclude (after seeing the data and the maps for the first time) that the expropriated land is necessary to protect Israeli citizens from terrorism.
I find it interesting that the organizers (Peace Now) apparently placed as much emphasis on getting the information to The New York Times--where it was reported prominently, and who actually spoke to the informant--as to the Israeli public, though they did, according to Ha'aretz, hold a press conference in Jerusalem. The American public doesn't already know these facts. The Israeli public is well aware already, and by and large, doesn't care.
Yes, this should cause an outrage, but it's just another one of those things that should cause an outrage that is all too common in this conflict and won't really change anything.