In order to prevent spammers from creating fake MB accounts, we should build a simple catcha system that is based on MusicBrainz data. To provide a catpcha, MB can pick any artist that has a known fact associated with it. Then prompt the user to look up that fact in MB and provide them a search prompt. If the user can provide the right answer, they are allowed to create an account.

e.g.

What city was Lada Gaga born in?

Accept answers: Manhattan, New York or NYC (via alias).