Not surprisingly, Caldwell has been a  critic of Twitter in the past. The Internet's largest vehicle for microblogging would have been better off as an instead of one centered on advertising, he says.

"We believe that advertising-supported social services are so consistently and inextricably at odds with the interests of users and developers that something must be done," Caldwell argues.

That point became painfully obvious to Twitter developers, who have seen the service on their use of its API.

According to Instapaper developer , Twitter's new rules for developers are designed to punish success. He said Twitter is telling developers,"Once you get big enough for us to notice, were going to require you to adhere to more strict, unpublished rules to make sure you don't compete with us or take too much value from our network."

Caldwell says his entry offers the opposite: "We're building a real-time social service where users and developers come first, not advertisers."