Thought parkin. One of the few metrics for evaluating content on the Web seems to be popularity. Easy to calculate, relatively, and seems to correlate with quality for at least "some" community. This is partially why folks love stuff like Technorati and Blogdex. (Is Blogdex even still alive? Does anyone care?).
What if you're evaluating a site, post, podcast, whatever, and you have no popularity information. Are there any other clues that might be indicators of quality?
One that comes to mind is consistency/regularity/reliability, which is why I liked the calenders that used to be on most blogs. You could get a quick metric of at least how long and frequently the author had been doing their thing. Skill improves with repetition so you'd presume that the longer you write/blog, the better you get at it. Plus it's an indication of commitment, which is an initial condition for quality.
Finally longevity and consistency is a metric a machine process could easily determine and might be something worthwhile for content recommenders to add in to recommended items.