Not sure who Trevor might be ;-) but thanks for the insight. You're right in that KPIs for blogging don't exist, and they are going to vary depending on what your goals might be. That's also highly dependent on how pervasive your brand already is, and what your target market might be.
While KPIs might not be applicable to every organization, they can be used for other purposes - such as gauging what kind of content is most appreciated by readers so you can do more of "that" and less of what they aren't interested in. So while you don't necessarily have to use those KPIs to "judge" success, they can be invaluable in providing direction and understanding of the audience and its needs.
Lori
