Also, Spain makes you fill out a green I-94W style form upon arrival which you keep until you depart. I don't know what you would do if you left the Schengen Area through another country. I've only entered/left through Spain or a third country in the Schengen Area. The first time they neither collected my form nor did I get an exit stamp. I don't know how that happened. I thought I might encounter problems the next time I visited, but the agent just stamped me right in. I did have an ORD stamp to prove I had, in fact, departed.

I would say the countries that are part of the Schengen Area are doing a lot more sharing of information than they were even a few years ago. There seem to be more and more posts about people being caught out of compliance than there were before. While you may think that the security is lax upon entering, they are doing a lot more behind the scenes work that you might not know. A friend of mine was pulled aside when he showed up to AMS two weekends in a row. (He was doing back-to-back MRs.) The first weekend he got stamped in with no questions. The second weekend he got sent to secondary for 30 minutes and had to explain to them why he was in AMS for a second week and his previous visit was only a day.

I didn't know that. But you can fly to Portugal and then travel by ground transportation, it seems pretty easy to me.

I also didn't know about forms, they imho doesn't make much sense since no other Schengen country wants them (at least those I visited so far).

I remember a member of tr.ru forum telling a curious story of how he managed to do a trip to France without having passed passport control a single time (cannot find the exact page though - it was quite a number of years ago).

He was a musician in a band which was to perform in some Alpine resort in France close to the Swiss border during Christmas feasts. It was the time when Switzerland already joined Schengen area but air traffic there was still extra-Schengen. The band were traveling from Moscow to Geneva via Vienna, so they were expected to be passport-controlled in Geneva and then proceed onto French territory; in Vienna they didn't leave the non-Schengen transit zone of the airport.

The weather was bad in Geneva, the flight was delayed several times, and the band was nervous about being late for their work. At last they departed, but at the very last moment the weather in Geneva became bad again and the flight was diverted to Grenoble.

What happened in Grenoble? In Grenoble they were happy to accept a flight from Vienna and did that so as if that was a regular one, i. e. an intra-Schengen flight.

The band's only thoughts at that time were about not being late at the resort where they headed to, for it might be a major financial loss if they missed their performance; so they only discovered that they were not properly stamped in on their way home.

However, in Geneva some other sort of miracle happened which he said he had no explanation for; they arrived there from the French side and after passing lots of long corridors found themselves on board of a Vienna-bound plane.

Thus he made a trip to France of which he got no trail in his passport.