Is it illegal to post someone's full name in your blog without their consent?

[Kyle Monk]

And if so what are the limitations? I see a lot of blogs that post facebook status quotes and block out the last name, why is that? Surely if they posted it, it is fact, so can't be construed as slander?

Pulling away from the facebook example... Say someone you knew, regularly beat their wife and this was a fact, could you legally then say on your blog 'John Smith' is a wife beater'. Would it depend on how wide your readership was?

Or is it a case of evidence, eg. He had posted multiple facebook comments saying 'I just beat my wife'. Or multiple Twitter statuses saying the same? Does the intended recipient of those comments matter?

If you were to post someone's full name in a blog discussing them and they were to find out, what would be the possible ramifications?

What makes a celebrity different? They are written about in full all the time, why is it different for normal people?

Would love some in depth answers if possible, I find privacy law fascinating.
To Jeff - I am asking from a journalistic standpoint, with the web 2.0 things have changed and a full name can give you access to many facets of a person's life.

One blog I occasionally read posts the full name and a link to the facebook of the person they are writing about, usually it is an expose on leud behaviour. I was wondering if that is legal and eitherway, what the line is?