Nearly a million tweets relating to the Barclays Premiership were sent in January 2011

"According to a report by Barclays, an explosion of Twitter activity saw close to a million tweets about the Premier League and its clubs in January, as fans took advantage of being able to 'follow' their favourite players, clubs and journalists and debate top stories as they happen."
[...]
"Most tweeted about Barclays Premier League teams
Liverpool: 301,169
Arsenal: 110,901
Chelsea: 97,655
Man United: 86,249
Spurs: 61,574
Cities with the most tweets about the Barclays Premier League
London: 263,988
Liverpool: 124,415
Manchester: 68,733
Birmingham: 20,112
Leeds: 18,514
and at the bottom...
Coventry: 499
Stoke: 450
Blackburn: 393
Wigan: 253"

Source:  Data from Barclays and Sysomos, reported by the Daily Mail, 9th February 2011

Note - I am assuming that this relates only to UK-based tweeters, where location can be identified.  Also, the presence of Liverpool at the top is probably due to two large stories (buying Carroll, selling Torres) rather than their fans being the most active tweeters