There's no defence for anonymous blogging in a society where freedom of speech exists. It is simply unnecessary. In a society like ours which enjoys free expression, whatever we say publicly whether on the internet, in writing or in speeches and broadcasts should be said in a spirit of openness and with complete willingness to take full responsibility for the consequences of what we say. Where the words and photographs of others are used to support opinions, sources should be clearly cited. Anonymity and misappropriation of others' material immediately call into question the motives of the person blogging or commenting. If someone is not prepared to put their name to what they write, is this because there is no solid evidence to back up what they are saying? Or is it perhaps because they know that their words will harm a person or a cause but they do not wish to accept the consequences of the harm they do? To say what they say may get them into trouble or lead to public outcry and criticism but that does not get them off the hook. The fundamental basis of debate in a democratic society is that of honest persuasion by identifiable agents. Yes, sometimes it's costly, particularly if you belong to an excluded or oppressed minority or if you yourself are subject to attempts at bullying or silencing. However, to retreat into anonymity only exacerbates the problem - the anonymous author becomes part of the bullying and oppression.
In a free society where human rights are protected by law, anonymous blogging and commenting is a form of literary and moral cowardice. It undermines and does huge damage to those who are trying to work in a transparent, accountable manner (sometimes even toward similar ends to the bloggers and commentators). Journalists are not averse to reading these blogs and being influenced by what they glean from people who are not willing to put their names to what they say. An analogy with hunting is not inappropriate here as victims of comment are sought out, publicly identified and pursued for a headline-generating story (which of course will not be reported under the protection of anonymity.)
Please think twice before you write or comment anonymously. Why do you need to do it anonymously? What are you afraid or ashamed of? Why are you hiding? Who might you be harming?
'And Jesus said to Pilate, "Sayest thou this thing of thyself or did others tell it thee of me?"'