According to a recent Google study with a luxury vehicle company, paid ads and organic search work together to create a greater lift in visitors.  This particular study concluded that adding branded ads brought a 12% increase in terms of driving visitors.  Just as marketing programs complement each other, the same is true for paid and organic search.  Marketers should evaluate - just because the brand is positioned well in organic does not mean you should ignore paid placement.  You could be missing out on potential opportunity...  in this case a 12% lift!   Of course you need to look at the investment side if you are adding paid search to the equation to ensure the return is there.  Of course a web analytics and bid optimization solution should be leveraged to ensure goal conversion is optimized to your objective.    
Source: Luxury Vehicle Brand Case Study; Google; GSD&M; July 2007