Since search engines seem to love blogs, would it not make sense to buy a link on a high ranking blog site? Especially if it's in context with your own? Would you either: a) Buy a text link on a PR 8 site with 5000 pages, but where the content does not change frequently b) Buy a text link on a PR7 site with 1000 pages, but where the content changes regularly because it's dynamic and growing?
Keep care to buy only without "nofollow" links. I would prefer 2nd option. also because of non-seo reasons.