I have a private Twitter account and use it as a personal diary of sorts. I see Twitter as a write-mostly device with some recall capability. There also happen to be 300-odd individuals who have read-only access to my diary. It's great to have them around, although my usage of Twitter is almost entirely not affected by my followers. On the other hand, the private nature of my account allows me to exercise tight control over who follows me. This lets me keep away the monster that is self-censorship.