Originally Posted by MikeMpls
When we went to Rome in Dec./Jan. (MSP-ATL-AMS-FCO) out passports were stamped in AMS but nobody said boo in Rome. We just took our suitcases & hit the road.
This is because the Netherlands and Italy participate in the Schengen Treaty--which doesn't recognize borders between all participating countries with respect to immigration (and customs). At present, there are 15 countries. Note that these countries aren't necessarily the same as the EU countries.
In your case, flying between Amsterdam and Rome is considered "domestic" for purposes of immigration (also customs)--equivalent of flying from, say, San Francisco to Denver. The reason you didn't get "boo" in Rome is because you entered in the Netherlands. Your bags, as was earlier mentioned, did not get the green stripes and as such, you're still subject to customs, though there's hardly anyone there to interrogate you. Your luggage, didn't go through formalities in the Netherlands (since they were probably checked "through").
Yeah, it's weird, but far less stressful than entering into the US.