From looking at how Google parses pages for snippets, I've noticed it does its best to ignore HREFs (i.e. blog rolls, nav links) that aren't embedded in unlinked text on the first pass. This behavior is probably completely unrelated to indexing pages, but its my way of saying that like Walrus pointed out, I believe blog posts that link to you are way more powerful than reciprocals links sitting lifelessly on blogrolls.
Aaron Wall recently laid out a few criterias for reciprocal links: relevance, traffic, and audience demographic, saying (I'm paraphrasing here) "link as if search engines didn't exist. Link for your surfers." Something like that. Don't get me wrong. I'm not endorsing what he wrote, but if you want some food for thought, check out
101 ways to build link popularity in 2006. I know adult sites are a different cup of tea than mainstream sites, but there might be a few good reminders on the list for bloggers.