why would Israel attack an ally? What possible benefit would there be to such an act?
Since the last release of information I have actually been inclining more to the accident theory, but there are a variety of reasons why the attack might have benefited Israel.
I think the most plausible scenario is that some of the Israeli generals, e.g. Dayan, were a little wild as good generals often are. They didn't want to take any chance that the intelligence collected by the US could be used in any way to restrict Israeli action. The primary thing that they were worried about was that if the US realized the vast amount of territory that Israel was conquering, there would be diplomatic pressure to end the war sooner. Thus some subset of the Israeli command decided to act first and worry about justification later.
Countries don't have friends. They have interests. Sometimes their interests diverge. Israel may have viewed this as one of those times.
Interesting theory...however, the war ended in 6 days. I had heard just recently that Russia had threatened to attack Israel if it went further than some specific date that coincided with the date the ‘67 war ended...