Guest blogging has been on Google's radar for some time, and this video from Matt Cutts is really aimed at anyone automating or spamming with "low-quality."
It's clear that Google are aware of the growing abuse and spamming, which means it's bubbling up on Google's list of techniques to tackle.
I read from this that if you're producing quality, you're not going to be on the radar. The worry is that even quality sites could be hit if a panda or penguin-like algo change or blanket penalty is applied.
What's your view on guest blogging and how it's being used?