When we switched to community server, back in April, I decided to stop moderating my posts, since the comment spam had reduced.
Well, over the past couple of weeks, I've seen a number of comment-spam attempts, which means that I'm likely to be a target again.
As a result, I've enabled moderation on all anonymous posts - if you're logged in, you won't be moderated, but if you aren't, your posts will take some time to show up.
Edit: Manip brings up a good point: To log in, go to http://blogs.msdn.com and click on the "Log In" link on the top left. You can also click on the "Join" link if you don't have an account yet.