The most effective young Facebook users, however—the ones who will probably be winners if Facebook turns out to be a model of the future they will inhabit as adults—are the ones who create successful online fictions about themselves.
They tend their doppelgängers fastidiously. They must manage offhand remarks and track candid snapshots at parties as carefully as a politician. Insincerity is rewarded, while sincerity creates a lifelong taint. Certainly, some version of this principle existed in the lives of teenagers before the web came along, but not with such unyielding, clinical precision.
I find that the biggest barrier to a reasoned debate is time rather than space, restrictive though it may be. Everything goes so fast that there is pressure to react sooner rather than later without allowing time for reflection. People then fall back on popular "truths" that can quickly be thrown out there. You can see this on Slashdot too where people pounce on articles to post the established group-think for a quick ' 5' (as well as the ubiquitous "frist psots".) Those who come relatively late to the debate will find themselves ignored and drowned out by the deluge of mindless babble. That said it's not like Twitter was meant for actual debate but more for stream of consciousness ego stroking verbal diarrhea. In that respect it is quite successful.