Either this guy is very lucky or something seems fishy here, how does he manage to get free hospitality by so many people to just invite a stranger to stay with them, I can't help but wonder if google is behind this somehow.
I can assure you, if you're friendly, the hospitality of others is endless. Particularly of note was Central America -- you could just get off at a bus stop, wander to the nearest cafe and people would be throwing themselves at you to hang out and chat. I had my guard up at first, but after a while it got so normal that it wasn't uncommon to find myself on some random person's couch/floor for a night/week here and there.
As for hospitality, people always seem to enjoy something/someone new in their daily lives - as long as you're friendly and don't overstay your welcome, you'll always find someone to show you the city and give you a place to crash for a few days.
Westerners (esp. Americans) are a curiosity and don't seem threatening at all (what with the smiles and politeness) - no Hungarian, Bulgarian or Turk will ever think you're a threat when you're alone and they've got a whole neighborhood to back them :-D.