Right now I limit the username format to: 3-25 alphanumeric characters with maximum 5 digits, 1 dot and 1 space. Could this interact with a Facebook/Twitter/Google+ registration? Say for example the Google+ name is "Jacques-Philippe Trepannier". That is more than 25 chars and it contains a non alphanumeric character not allowed on my regex. Will this cause any registration issues, or the Facebook/Twitter/Google+ registrations are not related to the regex conditions.