First, Technorati offers the ability to restrict searches to blogs of varying degrees of "authority". That can substantially reduce the amount of spam postings that come up in the search results.

Second, if you do a blog search using our search tool Zuula, you'll see that there's a lot of variety in how much spam comes up across the eight different blog search engines accessible via Zuula. Icerocket, for example, is quite good at keeping out spam, as are several others.

So it is, in fact, possible to take a do-it-yourself approach to blog search and still not suffer too much from all the spam postings out there.

Cheers!