Just curious but isn't this just digg, metafilter?

No, those are general-any link posting. This is more like Planet Mozilla, which used to be maintained as a curated aggregator of the personal blogs of contributors to the Mozilla project, which was not filtered exclusively to their Mozilla-content posts. Bubbles accretes on a different criteria than that, but at its core is similarly centered first around ‘curated authors’ rather than ‘curated links’, and then second around publishing all posts by a curated author. That curation is what makes it more valuable than a generic-any site aggregator like Digg or HN: a post by a curated human is much more likely to be interesting than the majority slop of /new on any content-first aggregation site (Imgur is a great example of this!).

Came here to say this. Perhaps it will work this time if it tries not to scale wildly, take investor money, and just do one thing well with a smaller group? But this kind of site has been around.