My brother once told me that weed makes his mind more sensitive. I thought that was interesting in regards to Stan Grov's commment on LSD as a nonspecific amplifier of the mind. I think THC is just a milder, nonspecific amplifier.
*If you're naturally social and like to talk, and you smoke, you'll be even more apt to talk and socialize. You'll become more extroverted.
*If you're naturally introverted and less comfortable in social situations, the weed is going to increase this introversion and make you even more uncomfortable when expected to socialize.
This becomes evident if you've ever had the misfortune of being mismatched in this area, where you smoke with someone, they become extremely talkative and you, even less than your typically quiet self (or vice versa) hardly can utter a word. Very draining.
I think its important to learn how to bring your awareness into the shared playing field of interactions with other people, and an equal interest in others as well as your own thought process...without altering your consciousness. I had to do this, having fallen into somewhat of a social rut in my later teens early twenties.
Edit: Sativa Indica deffinately plays a role
For me, climbing out of my mind and into the outside world was always more difficult with marijuana. This is why I only smoke it when I know I'll be alone, or, as said was before, when I'm drinking. Then it doesnt matter.