I use to be of the opinion that building backlinks (besides backlinks from search directories) was a "no-no" for local SEO. The potential irreversible damage to your clients' websites was just too great in my mind. I mean, we're not talking about affiliate marketing here, where if your website goes down, you just make another one. We're talking about Local SEO, where if any of your client's websites go down, it could mean their business. Who wants to be responsibly for that?
However, I'm starting to be tempted a bit with blog networks. Does anyone have any opinions?