Jack Dorsey, left, and Biz Stone of Obvious, the 10-person start-up in San Francisco that created the Twitter messaging service. Regular users of the service are called twitterers.Credit...Jim Wilson/The New York Times “ONLY connect,” the English novelist E. M. Forster admonished mankind. I don’t think, however, that he meant that we should connect exclusively, or continuously. Habitual users of a