Hey cstross, I almost added a link to your blog post at http://www.antipope.org/charlie/blog-static/2014/01/introduc... as an example of someone doing it right--you've clearly put a lot of thought into people who can add value for your blog's audience. You're at the very tip of the head in terms of quality--most of the scuzzy people take advantage of massive numbers of small, not-very-savvy bloggers who will throw up any submission they receive. So I wouldn't worry at all, and I apologize if my post came across too broadly.
beambot, I agree with your comments and adjusted the title of my post and added on to the end of my post to give more context. Certainly not all guest blogging is bad (e.g. valid reasons for guest blogging include exposure, branding, audience, community, expert opinions, etc.). We just see a lot of spammers exploiting guest blogging and innocent site owners as an SEO tactic, so I wanted to make it clear that we reserve the right to take action where we see abuse.