all of these can be changed, erased or dropped without changing who you are. Somewhat hard, but not much of a sacrifice involved.
On the other hand... Browsing patterns? Favorite geolocations? Depth of knowledge in differing fields, education, type of belief system, likes and dislikes in music, movies, sports, arts, philosophy, politics, rhetorical style, general attitude and personality that can be inferred from shyness, aggressiveness, type of humor, and so on and so forth? Most of these can already be cross-correlated to some extent (and the correlation algorithms/analytical engines will only keep getting better at it), and will draw a portrait of you that you will not be able to evade lest you sacrifice a significant part of who you actually are.
My personal take about this is one of general powerlessness, as justified by the history of how I used the intertubes. I started using the net when I was really young (10 years old, 1996) and left a huge real-name trail of info that squirmed and shifted through the years, yet always followed me. I began forming a deep understanding about the nature of internet quite too late (maybe around 1999), way back when I started lurking on slashdot, and then I had on-off phases of differing commitment to privacy, but I could always see that the trail had not dissipated behind me.
So I joined facebook and accepted that information wants to be free. I've found it easier and easier ever since, as I began ascribing to the motto, "if you don't think it, don't say it, if you don't believe it's right, don't do it". Thus I can be quite revealing online yet don't feel the slightest unease, even when I get into deep political/economical/philosophical/etc arguments. Sure, maybe some bible-thumper or political radical or such will get offended sometime, and try to give me trouble for it, but at that time I'll be happy to defend myself as I am proud of who I am and where I am going. So should some bureaucrat ever be offended at my omnipresent anti-fascist, anti-MIC rhetoric, well bring it on.
As E. E. Cummings once said, "to be nobody but yourself in a world which is doing its best day and night to make you like everybody else means to fight the hardest battle any human being can fight, and never stop fighting".