Link to great stuff often, and you’ll build an audience. But subsequent linkers don’t owe credit to every intermediate linker. It’s nice in some cirustances as a courtesy, but it’s never necessary. And even when a “via” link is included, most readers don’t care and don’t click.
My policy on attribution and linking is pretty simple: I try to link back to the article that led to me deciding to bring the topic to your attention. If I see a number of sites linking to the same original piece, I will typically give credit to whichever site I saw link to it first, unless I’m a subscriber of the site directly. If I am, then I’ll link directly without attributing a reference. So in the case of this piece, I saw it directly from the fingers of Marco on his site. For something like this piece on the EFF, it was Daring Fireball that I saw it on, so they get a link recognizing that.
Marco’s missing one big reason why these links matter: they are important to SEO and search engine placement, because they’re key currency in helping the search engines understand who’s influencing who and who’s writing stuff that other people find influential. As long as you don’t tag links with “nofollow”, your linking to the page or site helps Google and Bing understand which sites are influencing you, which helps those sites rank those pages and sites higher in their search engines. So even if nobody in your reader community clicks those links, they still impact the success of the site, so I think it’s important we at least try to make those links happen in situations where a site “earns” them (however you define ‘earn’).
It may not mean a lot to Gruber’s SEO that I link to his site, but it does help a little. In the case of a relatively small site like mine, it can make a big difference. My recent article on Aperture vs. Lightroom, for instance, got linked to by a few sites, and as of right now is the fourth link Google shows to people searching on “Aperture vs. Lightroom”. That’s driving traffic to that page so that right now it’s about 1/3 of my total daily page views, and THAT is causing some of those people to explore some other pages on my site. I expect that effect to fade over time, but for right now, a few (< 6) links have made a huge difference in site traffic, and it looks like some of those people are choosing to stick around.
That is why this kind of linking matters, not just whether people are clicking on the links while browsing. Few do, but the search engines notice, and that’s where all this cross linking and attribution pays dividends to those you give links to. And that’s why it’s worth the time to do it regularly, and put a bit of thought into how to do it well.