Tallon - 11:32 am on May 17, 2010 (gmt 0)
My MO is to retain as many visitors as possible so they return again and again, their word of mouth can (and do) more for me and reach in more deep pockets of the web than anything I can dream up. I don't care about where the links come from (twitter, facebook, forums, groups, blogs, email, nofollowed, followed, non-indexed, whatever)...they're all good for sending new visitors, and then rinse and repeat. A visitor may not link right away, but maybe next week or next month on one of their visits, or they may link every other week!
Google is a traffic sending monster, but it's amazing what an army of average web users can do for you. And Google seems to respond to that too ;).