Freedom & Blogs

When we blog, are we able to say everything and anything we want? What counts as freedom of speech, and where does the line get drawn? When we register to use a blogging service, is there any guarantee that the rules wont be changed at the site owners convenience? Even when the rules have been clearly defined and remain unaltered there are still situations where users have their blogs taken down or edited because of what someone else thinks is appropriate. Can we really expect freedom of speech with arguably public web space hosted on arguably private servers?