Most social applications I try out to are dumped rather quickly when they don’t serve any particular need I have. I joined Twitter out of curiosity to see what all the fuss was about as several infosec people spoke very highly of the system. I registered jeremiahg to give it a shot. A painless process. At first Twittering felt a little weird and awkward, with people “following” me feeling a bit creepy. Over time the value of the functionality became apparent and found myself consistently using the product. Twitter makes it easier to share thoughts and ideas quickly to get feedback from the crowd. Thats in addition to making it easier to track keywords of interest to others. Something blogs, email, and IM can't do proficiently on a personal network scale.
Email, RSS, IM, Twitter. Done.