Google's paid link detection algorithms keep improving, making it increasingly difficult to buy links. In a recent discussion at SES Chicago, panelists Todd Friesen, Doug Heil and Dave Naylor didn't recommend black hat tactics.
Eric Enge summarized the discussion by adding that Friesen and Naylor recommended starting with a few paid links to get a site off the ground. "Heil and I recommended engaging in natural link building from the start," Enge writes. "None of the parties recommended taking substantial risks."