August, 2011:

NoFollow backlinks aren't that useful, but people and Google do follow them. (Yes, Google does follow NoFollow Links, and in fact counts them a tiny bit for Pagerank.)

Also, it's possible that search engines may take notice of how many different domains link to a page. We don't know, but it's no more foolish counting backlink diversity than counting backlinks with no idea which of those backlinks are actually weighted as relevant to a particular search.

In that context, I was intrigued to discover through SquidUtils' Backlink Checker that when you build a shop on Zazzle.com, it propagates on Zazzle.co.uk, Zazzle.de, Zazzle.fr and Zazzle.pt. (Where's that?) Now, links in Zazzle descriptions are nofollow, so the backlink on my Mythphile Shop is not passing much pagerank.

Google is probably sophisticated enough to realize those multiple domains are not totally independent: they're obviously part of an international network of sites. Also, it sees the duplicate content. (I think the duplicate content scare triggered by Panda has set off a bit of hysteria... a few mirror sites won't send your content off the Google SERPs, it's just they may not rank quite as well, or maybe only one will rank well in each country. Oops, tangent.) Nevertheless, those links have to count as least as much as forum signature links, which Google is also sophisticated enough to recognize as (a) self-promotion, not an unbiased recommendation and (b) a forum signature -- multiple posts with it shouldn't be weighted any more, or much more, than a single post.

All of this means that you might as well open a Zazzle shop, if you've got some visual assets related to your niche.

What kind of assets?

Have you taken your own digital photos related to your topic? Are they photographs of public landmarks, nature, or out-of-copyright (pre-1920 should be safe) products or images? (See this "Legal Pitfalls of Using Photographs" copyright FAQ for more info on what's allowed.) Commercially-licensed Creative Commons images are also permissible, with credit and a backlink.

Consider making postcards or small prints with them. (Don't be misleading and print ordinary-sized images on a poster when the original picture is 600x800 pixels; it'll look awful blown up to poster-size.) Write keyword-rich descriptions. And tie it in somehow to your topic, as I did with my Mythphile Shop. Plant the backlink. It's not much link juice, but it's a little. It's worth expanding your online assets and footprint while creating a possible venue for money-earning.

(This is where I plug my Zazzle tutorial.) Anyway, it's a thought.