If I'm not mistaken, Google has all but said they seek to de-emphasize "unnatural" linking strategies, and recip links would fall into that category, would they not? After all, from a search engine's perspective in the ideal online world, a site would get links from others purely on the quality of their content and the perceived value to the linking site's visitors (relevance, etc.). I bet the algo looks at the % of recip links and de-values based on that. In other words, if 100% of my links are recip, they probably get severely downplayed in terms of weighting for rankings. If only 50% are, it seems logical that both the one-way inbound links AND the recip links would get more weight assigned to them. No?