The link it redirects to is http://twitter.com/worldcup/worldcup/ it seems like @worldcup was taken earlier so it has to go subpage.
Twitter does have pages like http://twitter.com/about but then twitter.com/user_name is usually a twitter account, it seems highly unlikely that twitter had reserved this http://twitter.com/worldcup/ earlier on.
However it could very well be a defunct account, so rather than over riding the @worldcup twitter took a subway it got to subpage http://twitter.com/worldcup/worldcup/ which is similar to the twitter lists.
There is a possibility of such a situation.
However it would be interesting to see what this page http://twitter.com/worldcup/ would link to once world cup would come to an end.
Twitter New:
The hashtags #worldcup and team name nicks {say fra for France} with a hash in front inserts a soccer ball image and team flag images in PNG format,
Note: These images are displayed in the text area on web interface of Twitter at http://twitter.com/
Note: The soccerball linking to http://twitter.com/worldcup/worldcup/ in #worldcup can only be seen while you are logged in however single tweet page would show the ball!
Try these links:
via http://search.twitter.com/ : http://search.twitter.com/search?q=worldcup
via hashtags search : http://twitter.com/#search?q=worldcup
Both would have yielded almost same results but now the results are very much different!
Note: search.twitter.com uses the acquired service Summize with some changes by Twitter.
You can see all the flags in this tweet by Mikko H. Hypponen {@mikkohypponen}
http://twitter.com/mikkohypponen/status/15921449874
