Blog search is in a pretty dire state, so any promising newcomer is likely to attract attention. In Sphere's case, it has been too much attention. The home page now says: "We're still in a limited private beta release and have temporarily stopped issuing new passwords because there is more demand than our feeble back end can handle."
In the meantime, you could follow the home page links or read the post on the Search Engine Watch blog, which says:
Sphere takes a new approach to blog search, looking at three critical variables to understand both individual blog posts and the nature of the blog they appear on. As with web search, Sphere attempts to understand link structures--who's linking to whom, and what are the quality of the links. Crucial to this analysis is an attempt to understand who's starting or leading discussions in contrast to those bloggers who are simply commenting on existing conversations.
Sphere also looks at meta data--things like posting frequency, lengths of postings, and other non-keyword related data.
And finally, Sphere's algorithm content does some heavy lifting with semantic analysis of blog postings. "It's the hard part, and most important piece of the secret sauce," said Sphere co-founder Steve Nieker.
Screenshot from Yahoo's Jeremy Zawodny
