My question is: How valuable are these links, if they are coming from "new" domains (since they are subdomains), and they only have a few backlinks pointing to them? Would it be more effective to spend my time with other link building methods? Many people say that relevant links aren't really better, and that it's only a myth.
Secondly, if this link building technique IS worthwhile, couldn't I essentially get the same link juice by purchasing 10-20 domains, hosting them on separate IPs, and then making a subdomain on each domain for each of my campaigns so I don't have to rely on these web 2.0 sites? I would obviously make sure I didn't leave any footprints in this scenario.