I think we're going to see more of this kind of thing. Bandwagon is offering free accounts to bloggers who post their logo (see left), link to their site (see previous sentence), and send a trackback to their blog. This offer lasts until 22 February, so if you're a blogger and want to take advantage of it, be quick about it. (I found it via cityofsound.)
In my book (sorry, you're going to get sick of that phrase if you keep reading this blog, but it's part of the deal here: I have to promote it) I speculate about a scenario where, instead of gig promoters handing out flyers saying "£1 off with this flyer", they will blog on MySpace etc saying "£1 off with a trackback to this blog". It's a handy and easy way to enlist your audience as co-promoters. In fact, I suspect this may not be a future scenario; it may well be happening already. Does anyone have any examples they could point me to?
I'm also interested in how these kinds of blog promotions affect the much-vaunted authenticity of 'blog culture' — something I've written about before here and here. The you-scratch-my-back-and-I'll-scratch-yours deal offered by Bandwagon is not quite as directly commercial as, say, PayPerPost (which only recently started requiring bloggers to disclose the payments they receive), but it clearly introduces the scope for bias and dilution of authenticity.
As for Bandwagon's service itself, it's a useful model. I'm not sure whether I'll use it, as it requires iTunes 7, and I've avoided upgrading to that since my creaky old iMac struggles even with iTunes 6. I use an MP3tunes locker, which works for backing up your music files from any version of iTunes and any platform.