Palestine Times has a photo essay of how Palestinian Arabs in Lebanon live in squalor:
If there is any issue that unites Lebanese - right or left, religious or secular - it is that these Palestinian Arabs must never become citizens of that country. There is institutionalized discrimination against them, as they cannot move out of these camps, they cannot expand them, and usually they cannot even build within them.
This is all separate from the many jobs they are not allowed to take, and that they cannot buy land.
There is even a religious aspect to this. Practically all Palestinian Christians did manage to become Lebanese citizens, mostly in the 1950s and 1960s. But the Sunni Muslims, for the most part, did not (unless they could convince officials that they had Lebanese ancestry.)
This, ladies and gentlemen, is what apartheid looks like.