Twitter is a unique experience for each user. for me, i only follow "people" of interest and rarely contribute. when looking at my twitter, you won't find "just brushed my teeth" or "heading out now" comments from friends. you'll find updates on local events, free beer and food offerings, concert schedules, news and weather...
it's also the most immediate way to get information to a large group of people. the band Phish is back on tour and their fans always want to know the setlist of the show that was just played. we used to wait days. with twitter, we're getting realtime updates, song by song, as they're played.