Most links on spam blogs usually have backlinks to other spam blogs. When I run the backlink checker (I usually only post 200 links at a time), I only save those with 1000+ results, because I figure they must've used a program like Scrapebox to get 1000 or more backlinks. And to answer your question, the Blog Analyzer checks whether the site can be posted on or not. Run the analyzer, then post to the sites that can be posted on, run the link checker right after, and save the ones that are found! Unfortunately, even after checking about 100k blogs, only like 5k stick (for me anyway).