Sorry to jump on your thread, but out of interest is there any particular blog sites (tumblr/wordpress etc) that people prefer to use for this type of blogging? Similarly do you actively promote your blogs elsewhere so as to increase their exposure to the SEs (as presumably if you don't then they'll never get a good ranking so the backlinks to your main site won't be much help anway). If you do this then what's the real advantage of having a blog rather than just creating a page on your actual site focused towards certain keywords and doing the link building to that, surely that would be more effective?
Just thought i'd ask as it's always confused me slightly the real value in setting up other blogs to promote ones main site, i hope you don't mind
Dave