Stephen mentions a couple interesting problems in blog search, timeliness (old news is no news) and relevance rank. Here is an excerpt on blog search relevance rank:
The challenge, though, is figuring out which posts should rank atop the results. Should it simply be the most recent? Or from a popular blogger? Or perhaps a blogger already bookmarked by the user, or even by those on the user's buddy list?From current blog search engines, it's just the most recent posts that make it to the top. In the future, it will have to be more.
Readers want to see the most relevant, useful, and interesting news quickly and easily. Sorting by date isn't enough, not with millions of spam blogs, personal diaries, and junk blogs out there. Sorting by popularity or reputation is getting closer, but it discards the best part of weblogs, the sparkling gems stuck out in the long tail. Sorting by what your friends like or using a social network might work if everyone has an extensive network, but most people won't bother with the work of setting that up.
What you need is a way to sort by what is most relevant to you. You need a system that surfaces the blog posts that are most interesting to you and people like you. You need a site that learns what you like and focuses you in on the gems. You need a personalized relevance rank.
See also my previous post, "A relevance rank for news and weblogs".
[Found on Findory]