It all depends on your intent. And there's an infinite amount of nuance in these situations. Of course, you shouldn't aggressively hit on every person you interact with but chatting strangers up? Absolutely.

The beauty of life is randomness and spontaneity; meeting new interesting people. But you have to be desireless, and non-intimidating without any agenda. Not consumed with the thought of capitalizing on the relationship somehow, be it sex or business networking.

I strongly disagree with the sentiment expressed in your comment and to me, it is slightly depressing. I suppose part of your logic is due to brash American guys hitting on every girl, but putting that aside, I do not want to live in a world where every interaction is clinical, and devoid of depth, of magic, and optimized for the efficiency of the economic transaction.

I want presence. I want more interconnectiveness; discovery and mystery; laughter and love. In all areas of life, in every moment possible.