The challenge of identifying the authority of a blog was raised yesterday at econsultancy’s Online PR roundtable.

Technorati recently changed its blog authority ranking to reflect the real time potency of a blog rather than influence over time. Consequently only very high profile blogs are being rated.

The number of inbound links combined with Google PageRank was proposed as a solution at yesterday’s roundtable.

AdAge uses an algorithm based on PostRank, Yahoo InLinks, Alexa Points and Collective Intellect to generate it Top 150 league table. Author Todd Andrik also adds a subjective measure based on frequency, relevance and creativity.

Edelman’s Jonny Bentwood proposes a ranking methodology based on a broader range of variables. These are Google PageRank, inbound links (via Google and Yahoo!), RSS subscriptions (via Google Reader), frequency of postings and most recent post, comments and inbound Twitter links.

How do you measure the authority of a blog?