To reproduce:
1) go to http://geordi.musicbrainz.org/login?next=%2F
2) enter a username that doesn't exist (I chose the superb "askfnaskgfdjnkladfgjd") or don't enter a username at all
3) click 'Go'
4) If you're not logged in on beta.mb, do so now
5) Check http://beta.musicbrainz.org/account/applications, it contains one additional entry

I'm not sure if this is really a Geordi or an MBS issue, please move accordingly.