This current version includes redundant stuff because of previous export processes that allowed just the relevant databases to be included. These are easily skipped or deleted from the Text-only results when you past the results into a new query, such as http://data.stackexchange.com/stackoverflow/query/69701/emailhash-comparison. Note the December 2012 export includes some EmailHashes that are case sensitive and some that are case insensitive, so I COLLATED all comparisons rather than working out which is which.
Q&A for network engineers
Select 'Select ''' + Replace([Name],'','') + ''' As [DatabaseName], '
+ 'Count(*) As [Count] '
+ 'From [' + [Name] + ']..Users fu Join Users u ON fu.EmailHash=u.EmailHash'
+ ' Where ISNULL(u.EmailHash,'''')<>'''' COLLATE SQL_Latin1_General_CP1_CI_AS'
+ ' UNION ALL '
Where Name Like '%'