Many iPhone users have been criticizing Apple for not integrating social networking support in its OS. It seems Apple team has heard the demand of end users, as some people have found out the evidence of Facebook integration in iPhone OS 4 beta.
This could possibly be mean that final version of iPhone OS 4 will come out with unified Calendar and Contacts apps, which will have Facebook integration for social networking lovers.
Screenshots of Facebook Integration in iPhone OS 4
[via - Engadget, source - Gunning For Safety]