The amazing thing about twitter as a platform and community is that it’s evolution has come through it’s use. Through use, people together evolve new ways of communicating. The #hashtag, the retweet, the @reply, follow friday, trending topics, real time twitter search, explaining twitter trends, cc-ing users, etc… These were all creations of the user base, people tried out ideas and built them. Twitter the company later adopted the conventions of it’s community and formalized the tools. This letting the community of users create, and then adopting the practices is critical to how Twitter’s grown to be such an amazing platform.
Great post from Rabble on the history of the @ reply.