It was only a matter of time before it became official.  Link building via guest posting is officially dead.  Matt Cutts came out on his blog a few days ago finally changing his stance from sparse, high quality guest posting being appropriate to the act being completely dead in terms of SEO in a matter of months.

You can read the post at the following link :

What does that mean for people building links off of InfoBarrel? We aren't 100% sure yet.  However we will definitely be tightening up on any posts that are clearly written for the sake of building links.

We will keep everybody in the loop with any changes as things unfold.

Check out the conversation on the forum.