Many olim from western countries like the US would think twice about making Aliyah if it meant giving up their duel nationality or even having their passports marked. Things like American citizenship and an American pasport are much more useful on a global scale than Israeli. I hold a British passport & an Israeli one - the British one will allow me to waiver the need for a visa if I wanted to go into countries like the US because the UK has a visa waiver scheme Israel does not. Its also very convenient when it comes to visiting the UK because I go through the passport control for nationals rather than tourists and its usually quicker. I enter and leave Israel on my Israeli passport. Marking passports or refusing duel citizenship wouldn't solve the problem Mossad would just forge passports which they have the facilities to do. Using diel nationals is more convenient but forging is not a problem. Chris whilst your acting all high minded remeber your country spies on other as well.
19-year-old construction worker seriously injured after falling from scaffolding in Harish (Haaretz)
from the article: Report: Mossad used Australian passports before Dubai row