validates_uniqueness_of :nick, :if => :nick validates_uniqueness_of :openid, :if => :openid These don't allow multiple blanks. Use :allow_blank for that.
Could not reproduce problem with many users having empty nick/ openid. Test specifically for that: https://github.com/ahenobarbi/Gentoo-Recruiters-App/commit/5deaf111d9ea5b2d7882f3ab1970a36211461287
Confirmed, fix: https://github.com/ahenobarbi/Gentoo-Recruiters-App/commit/37c43b0d64ee321f0419b098f26e756dc2712661
Fix was accepted.