This site is perhaps one of the easiest sites out there on the Stack Exchange network where a tag predictor could be implemented.
How does it work?
By the time you finish writing a question, the space below the "Tags" textbox would show a list of tags you would probably want to use.
Why is it useful?
Saves precious time in digging for the tags needed
I believe this website would be a starting milestone for Stack Exchange engineers, for testing their tag prediction system, as they move on to implement tag prediction on their more complex communities.
Why first here?
Most of the questions on this site ask about one sport at one time, and the name of that sport is repeated at least twice in the question body, so that makes it an easy guess for a machine to guess what tags would be used.