Recently, I've sent invites to a bunch of my friends using the feature provided on Blogger.com, not realising that it's actually a feature that gives out authoring rights on this Blog, which is why you get asked to register prior to posting. Just ignore that.
Messages can be posted on my blog without needing to register or make an account.
Sorry for the inconveniences caused! I'm still very new to this blog thing. Next coffee's on me! :p