American Strangers Vs Indian Strangers

Americans have this interesting culture of putting up a conversations with strangers. For ex. when I'm on an elevator, any American in the elevator would come out with a simple expression like "How're you doin today?" or part with a wish for a good day ahead.

Had there been a fellow Indian in the elevator, whom I didn't happen to know, he'll have the most serious expression possible on the face. Even if I attempt and have a smile on my face, I get back only a weird inexplicable expression. If it's an Indian lady, the expression would just fall short of the one given to a scoundrel.

There is a reason probably for this to happen. When I have a nice friendly smile on my face, the fellow Indian must be thinking to himself/herself "Is he an Amway guy?" or "Why is this guy smiling at me? Surely he must be upto something".

Many times I reciprocate to Indians with a smile , only to find that it was an encouragement for the guy to come up to me and ask if I am interested in making 'extra' money, 'over and above' my regular income, by listening to his business propositions. Sad state, but have to live with this.
For instance, there is this guy, who has approached me atleast 5-6 times in different places like the library, the Indian store, Indian Restaurant etc, with a typical opening statement like "Do you stay in XYZ apt?" or "Have I met you somewhere before?". Each of those times in the past, I patiently declined to have met him before. It happened again today in the Library, and I had to give it back on his face saying "You must have asked me this question... God knows how many times". Not having done such a thing ever before, I just turned around and moved without waiting for his reaction. Poor fellow, he won't forget my face from now on, and probably will make an effort to remember faces which he has already given a shot with his propositions!

I guess life would be boring without all these little incidents....