I see the eternal September as part of the natural life cycle of a user-driven site. It begins as a small, niche community focused around certain interests and types of discourse. Content that gets pushed to the top is the content that's most popular, which has the effect of catering to the lowest common denominator. Therefore, as the user base grows larger favored content tends to be what requires the least effort to appreciate. Hence, more people who like easy to appreciate content will be driven to the site, i.e. almost everyone on the internet. Reddit's advice animals are the perfect example of this. They are easy to create and can be understood by anyone. They take zero intellectual effort to produce or consume, yet they appeal to broadly appreciable emotions and experiences, so they're easily rewarded. Naturally, if advice animals are what gets promoted on reddit then more people who like that sort of thing will come there. Quality degrades exponentially. The old users no longer have their niche community that caters to their specific interests, so they leave.

Maybe the structure of Hubski solves some of these problems, maybe not. Or maybe Hubski will never become popular in the ways reddit, digg, or even 4chan did. I guess we'll find out.