Beside the obvious, that Obama altered the negotiating rules and premises in the peace process, I've had an a-ha moment about Obama's use of the ‘67 borders. He's also reversed the negotiating roles that the US has continually upheld in its support of Israel. In so doing, he has betrayed the historical alliance with Israel and elevated the role of the PA to new and unearned heights in the negotiations.
As we know, previous administrations have started negotiations in terms of a withdrawal from the territories -- just as UN Resolution 242 calls for. Under this formulation, Palestinians get their state through subtraction from the whole, an Israeli withdrawal that begins with/from the full territory it now "occupies." As Resolution 242 states (and regardless of the amount of territory), a peace settlement calls for a "withdrawal of Israeli armed forces from territories occupied in the recent conflict." Obama has, in a single speech, altered the premise of the peace process. Obama's new formula begins with the 67 lines which means that the Palestinians (explicitly) get their full West Bank territory to start with. With this formula, the ‘67 lines, it's now the PA that gets to "subtract" from its territory and Israel that has to add on territory. This has the effect of completely reversing the roles of the negotiating actors, Israel and the PA, that previous presidents had maintained. It also manages to undermine what is even a sometimes controversial document in its own right, Resolution 242, which at the very least calls for an Israeli withdrawal from territories, and not obviously a Palestinian one!
In short, previous presidents have worked by building PA control and sovereignty over the West Bank and Gaza, which happens in more recent times to be the basis of the Oslo Accords. This president is speaking in terms of a full Israeli withdrawal and leaving not the PA but Israel in the position of having to "add on" or build up territory. With Obama, it's PA that starts with a more "sovereign" territory (the West Bank) and it thus becomes the partner who "subtracts" territory. Why is this problematic? The PA has never been the partner who subtracts territory. It's been on the receiving end of land. That's what Land for Peace means. That's what's different about his use of the ‘67 lines. It's not just that he said it as if other presidents hadn't. (Though if they had, then like the "torture memos" they should find a way to release those statements too.) By reversing the territorial roles at the negotiating table, Obama has undermined its long standing ally, Israel, and has switched instead to an implicit pro-Palestinian stance. Obama's policy, and what should worry Israel supporters, calls for a complete reversal of the meaning and historical legitimacy of the negotiating roles since Israel was attacked by the Arab states in 1948. Obama's call for negotiations premised on ‘67 lines is nothing less than a denial of the U.S. understanding that Israel won territory in self-defense, and, in accordance with Resolution 242, has always looked to return such land to a willing peace partner. It's not for the PA to make territorial concessions in qualitatively the same way as Israel. But that's what the ‘67 line ultimately demands; it places the PA not just on morally and politically equal footing as Israel, but also on territorially equal footing -- something that no president has ever done. It's a role reversal of the most deceptive kind. But it's how Obama has turned himself into the pro-Palestinian president.