Before the handover of Gaza, access to Gaza from Egypt had been a problem all along the Sinai border to the point of tunnels being constructed.
Assuming that maintaining security along the entire Gaza border was untenable, by establishing what would appear to be an open door, with proper monitoring (which is what apparently failed), Israel can be more aware of what is coming into Gaza through this "friendly" gate. All of Israel's access points along the "green line" fence face threats on a regular basis, and it would not be unusual for bombs to be (attempted top be) smuggled across at any of them --- especially out of Gaza--- regardless of who monitors the Sinai border.
Ideally, Israel would still be in full control (were they ever?) of Gaza and destroy the terrorist militants once and for all, but this hasn't happened up until now, and I don't anticipate it being a long-range/long-term option.
So Rice made sure the terrorists no longer had to work hard. They can just drive in.
Rice for President. She takes the terrorists for a ride.
Ah, so this must have been the reason to throw 8000 Jews from their homes. Good thinking.