Similarly, Michael Arrington builds trust by often mentioning Om Malik (GigaOm) and Richard MacManus (Read/WriteWeb) on his blog. I suppose it leaves the feeling that "He can't possibly promote a rivals blog without having a better one himself!"
Ironically, a few weeks ago, Scoble mentioned that bloggers are geedy when it comes to linking (he mentioned Engadget/Gizmodo as an example, and that sure did piss them off). I think I will go ahead and forward this study to him :)
That said, I would be interested to know how they conducted this study. From the looks of it, it seems they simply compared a site's worth versus # of outgoing links. The fact that we agree with the study might just be a placebo affect.
In the case of bloggers, though, there is another effect in play: blogs succeed basically on connectedness, so for a new or up-coming blog, the most important thing is tying into the network of existing blogs in the relevant domain. It makes sense that praising, referencing, critiquing, generally interacting with "competing" blogs is the best way to jack into the community.