Microblogging is a ‘‘Mobile Web 2.0’’ service category that enables brief blog-like postings from mobile terminals and PCs to the World Wide Web. To shed light on microblogging as a communication genre, we report on multiple analyses of data from the first 10 months of a service called Jaiku. The main finding is that microblogging centers on selective, I-centered disclosure of current activities and experiences, making daily experiences visible for others. The high frequency of brief and mundane status updates, like ‘‘working,’’ may be a second-order effect resulting from posting becoming a routine executed to keep the audience interested. The results highlight the importance of reciprocal activity and feedback in users’ motivation to invest in this activity. Keywords Microblogging Á Self-disclosure Á Mobile services Á Jaiku