You should probably not go to the US with a passport full of African and Middle-Eastern state stamps these days... In fact, back already in 1999, we were allowed to have two passports (same number and same name) when travelling a lot, in order, officially, to have the time to getvisas from countries that took their time, but in reality to be able to travel to sensitive places without compromising the ability to travel to places that worried about these. I have a passport with stamps from Iran, Turkey, Syria, Lebanon, Turkmenistan and 10 pages of Russian stamps (in fact, there's no available space on it anymore); it's no longer valid but I'd be curious to see the reaction of Homeland Security to it...

As to missing stamps, I did manage to get into Russia once without getting my passport stamped (I took the night train from Kiev to Moscow), but I did get the exit stamp without a problem. I also managed to take a Lebanese rental car into Syria, something that was apparently strictly forbidden, but which did happen (and that's when I discovered that there was no unleaded fuel in Syria -back in 1997 - so we had to limit our driving around; we ended up staying in Hama and rented Mercedes taxis for daytrips while we were there). But I do have a detailed stamp in the passpost wit hthe car registration number on it... btw Syria was the one place where the personality cult was creepier than anything I saw in the Soviet Union and Former Soviet Union.

In the long run, we're all dead. John Maynard Keynes