I don't think that bloggers are necessarily pulling punches on their posts. They're getting better at what they do, regressing to the mean slightly, and writing for the audience that's made its voice heard on their site, IMHO.

Blogging means many things to many people. Some use it for expression, some for business, others for ranting, and dozens of other reasons. I believe that we're at a point where those that have been blogging for some years now are 'maturing' in the 'blogging lifecycle' and their writing is reflecting that. Do I have data to support that, not really, but it's a thought that I think holds some merit.

Personally, I know that my blogging has changed due in large part to one factor: Audience

If I have an audience that I'm trying to retain, I start to figure out what drives my numbers, and there are few among us that don't like looking at their stats and see the numbers going up when we write something that resonates.