JakeWharton/trakt-java — pull request #42 by UweTrottmann (2012-07-22 21:13:42+00:00)
Title: Do not encode user name

Trakt does not support URL encoding application/x-www-form-urlencoded as
used by URLEncoder. Mail addresses however require the @ symbol to be encoded to a %xx format on which the trakt API returns a failure stating 'bad user'.

I'm not an expert to see possible ramifications here, so take this one with a grain of salt. Maybe the better way is to ask trakt to support the above encoding.