Phatic communication--what's up?

I've been thinking that I want to do my final research paper on something that has always bothered me (and yet it's still something that I do with some frequency). I never realized that there was a name for it until it was on Dr. Ray's list of recommended research topics. After some quick Wikipedia research, I realized that phatic communication is something everyone does (with a few possible exceptions of ultra-aware speakers/writers).

Just this morning, my roommates and I greeted each other with "good morning," even though it was technically afternoon. Were we really wishing for each other to have a good morning, or is that just what's socially acceptable when one first greets a person in the early hours of the day? It seems to be the latter.

This is especially prevalent in the context of social networking. People who aren't even "friends" will use small talk in order to not forget about each other, it seems. Are there other purposes for phatic communication?