Topic blogs with RSS

Artima Technology has set up a nifty experiment using RSS to create aggregate blogs for techology topics like Perl, Python, C#, agile development, patterns, and more.
Bloggers submit their blog and choose which of 26 topics their blog resembles most closely. The problem is, most bloggers — even bloggers who write a lot about a single topic — tend to write about more than one thing.
So, the Java blog page contains an entry each on geocoding for weblogs, HTML encoding, Movable Type, XML proliferation, and Echo, along with nine posts that actually mention Java!
I prefer the Trackback method of making topic blogs. The author categorizes the post s/he wants to contribute instead of having to stereotype the entire blog with a single topic.
This makes the blog much more relevant and focused. The Austin and Seattle community blogs use this method, and I’ve seen good conference blogs use this method, too.