Elephant 1: Hamas controls Gaza
Every peace plan includes Gaza in a Palestinian Arab state, and none of them has any provision on how to handle the fact that Gaza is a terrorist haven, in much worse shape since Israel uprooted the settlements there, controlled by a terrorist group that has no interest in restraining the even-more extremist terror groups that thrive there. Peace is impossible with this elephant, so it is easier to pretend it isn't there.
Elephant 2: Palestinian Arabs elected a terror government
In the only fair, democratic elections in the territories, the Hamas terrorists were chosen by the people. Poll after poll shows that Palestinian Arabs support terror in Israel itself. The elections proved that the conventional wisdom was wrong - and the conventional wisdom proceeded to ignore it.
Elephant 3: The current PA government was not elected
This corollary to Elephant 2 means that the current people negotiating for the Palestinian Arabs do not represent the people. Even if they sound moderate or compromising, they have no mandate. Negotiating with them is, literally, meaningless.
Elephant 4: The current PA government has almost no power
Outside of Ramallah, the Fayyad/Abbas government has little popular support and little power. The Nablus "clean-up" was an orchestrated fiction, as was the recent high-profile "surrender" of nine Al-Aqsa terrorists - who are now due to become upstanding, paid members of the security forces in three months.
Elephant 5: The PA is being kept alive by artificial methods
The PA budget is bloated from "payroll" of non-working workers - but if they would slash the payroll, the people on intrnational welfare would revolt. So the very basis of the organized Palestinian Arab workforce is a fiction being kept barely alive by ever-increasing infusions of cash with no real plan to fix the problem.
Elephant 6: Fatah remains a terrorist group paid by the PA
Despite the recent claims that the Al Aqsa Martyrs' Brigades has dismantled, it is a joke meant to appease the wishful-thinkers. There has been no serious move by the PA against terror except for its tit-for-tat arrests of Hamas members in the West Bank, and its moves have been almost wholly cosmetic and aimed for Western consumption rather than real fighting against terror.
Elephant 7: The first - and second - stages of the roadmap were never implemented
The entire point of the road map was to slowly build confidence, starting with the end of terror and incitement on the Palestinian Arab side, afterwards building a "provisional" state and only then going to final-status negotiations. By skipping to Phase III as if the other two phases were already in place, the entire exercise is simply a joke. Incitement remains at full blast and the slight lull in terror is tactical, not a sea-change in Palestinian Arab attitudes.
Elephant 8: The PA's goal remains the destruction of Israel
Whether it is by "right of return" or not changing the Fatah charter or by printing map after map showing no Israel, even the most moderate Palestinian leader clings to the idea of destroying Israel, and looks upon a Palestinian Arab state as only one stage in the process.
Elephant 9: Jerusalem
Most Israelis want a unified Jerusalem under Israeli sovereignty. Most Palestinian Arabs refuse to accept anything less than all of Jerusalem as the capital of a Muslim state. The positions are not compatible and a compromise will not reduce the chances for violence - it will increase it.
Elephant 10: What happened to Gaza
Forgetting Hamas for now, the time period between Israel's dismantling settlements in Gaza and the Hamas takeover is instructive as to how Palestinian Arabs take advantage of territory they gain. They didn't build new houses or communities to reduce the "refugee camp" population, no schools or hospitals. They destroyed the greenhouses purchased for them by American Jews; they turned beautiful former settlements into training camps for terror - in other words, Israel's last major concession not only didn't help achieve peace, it ended up encouraging terror. Any claims that something similar wouldn't happen in the West Bank is the triumph of wishful thinking over experience.
These are off the top of my head - any others I should add?