For those people who do use the features on their power/smart/mega phones, you'll less-than-3 Twitter. For all the bagazillion things the Internets offer, Twitter is the one that makes the most sense in the translation from PC to phone (okay, maybe it's in a tie with mapping/GPS applications).
Twitter gives you that sense (be it quasi or genuine) of being connected, and the quality of the experience is by no means diminished by the limitations of your phone. It's actually enhanced, because, unlike PC-based functions that require you to be home* on a Friday night to hang with your e-friends, phone Twittering allows you to maintain your virtual network while also enjoying an actual life. You can have your geek and eat out, too.
As for me, I'm still sitting when I'm twitting. But for those of you with lives, take heart. Twitter (and all your techno tweeple) can follow right along.
*or in your dorm room, library, office, or the local Panera where you and your laptop are usually stationed