Here's how he described the service in a 2010 column:
Like many newbies on Twitter, I vastly overestimated the importance of broadcasting on Twitter and after a while, I realized that I was not Moses and neither Twitter nor its users were wondering what I thought. Nearly a year in, I’ve come to understand that the real value of the service is listening to a wired collective voice.
Alone, each message about Carr's passing showed just how much he and his writing meant on a personal level to readers, colleagues, and everyone else who strung characters together to describe the pain of his passing.
But together, the outpouring becomes something more — a chorus that pushed the writer's name to the top Twitter's "trends" box and amplified just how acutely his voice will be missed.
Thursday night, the wired collective voice of Twitter howled "David Carr."
Update: Here are a few more Tweets.