In my brief stay there, I found the Turkish to be similar to those in other Muslim countries I'd been to (Egypt, Jordan, Syria). That is, extremely hospitable and often very generous. Some will try pamper you with some sort of expectation of getting something in return (ie. you buying something of theirs or tipping them).
Others, however, will be very generous and not expect anything in return. They perhaps just like to befriend someone who is from a different land, and/or may want you to have a great stay in their country. Maybe they feel that there is some duty for them to do this - which is a great quality for us travellers!
Some might be that good at being nice, acting genuine and taking you in that you'll end up giving them a gift in return and be pondering what their intentions were for an eternity 
As for your case I think you'd have to go with your instincts and judge their character, but keep in mind that a lot are genuinely very hospitable so such a thing wouldn't surprise me. One key thing is probably how long it took them to offer you accomodation, if they did it straight away there's more chance of there being a catch, if it was after chatting for a long time it might be genuine.
I can't think of a catchy slogan - but I reckon it should be along the lines of their hospitality and courteousness.
That or their die hard ambitions of being part of the EU 
[ Edit: Edited on Dec 29, 2008, at 9:18 PM by Erik85 ]