What with the Pope wandering around the Holy Land, the New York Times offers a recap on the story of the Christian Arabs in the Middle East: There are hardly any left. All across the Arab world, Christian Arabs were often more modern, better educated and more affluent than their Muslim neighbors, all of which made it easier to emigrate. Once they began to do so, there were also communities of them outside the Arab world to which it was then easier to immigrate. Also, being Christians, it was often comparatively easy to put down new roots.
It might also be useful to mention that the Muslim world has less and less patience for minorities, even if they're Arabic-speaking, ethnically Arab and have been there for thousands of years, in many cases longer than some Muslims who arrived in various waves starting in the 7th century. So there's a push and pull dynamic.
None of this is new, of course; it's an old and worn story. Still, it's worth repeating, if only because quite often people note the diminishing Christian-Palestinian population and chalk it up as yet another crime of Zionism.