Social Networking identity vs. real world identity

One thing I found odd about the Boyd article is that it seems to equate the socialization on social networking sites with that in the real world.  I personally find the two to be extremely different--in a social network site, your profile is not a description of you so much as it is a description of your tastes (music, movies, etc.), in a social networking site all conversations are written words which do not have the added complexities of intonation and body language, etc.  There are inumerable differences between the online world and the offline, and because of that, I think it's not necessarily safe to assume that socialization into one will entail the same for the other.  While their early initiation into the public sphere via social networking sites could lead to the current generation being more comfortable with the public sphere and more competent in wading through offline social networks, couldn't it just as easily be the case that people socialized into the rules of online social networks could find themselves hamstrung by these rules as they are completely different from those of the real world?  I'm not saying that the latter would necessarily be the case at all, I'm just playing devil's advocate as Boyd did not seem to take this option into consideration. 

Also, a separate thought--I wonder if the fact that social networking sites so strongly tend to highlight tastes in things (music, movies, etc.) as part of their profile pages is not only a remainder from their dating site origins, but is done out of commercial interest--i.e., defining a person in terms of the things they like strongly supports consumer capitalism, and pushes people to buy more things, and to equate these things with their own identity?