Today, I read through a great slide deck put together by the Weiden+Kennedy agency called "How to (not) Fail." It is 110 slides long, and goes through several thought provoking points. I definitely recommend you read through it.
The one that stuck with me is about the effect of Brand Advocates starting on slide 44. The author, Martin Weigel, starts with saying that relying on devotion is the path to failure. He backs that up with two slides showing the sales of Garnier Fructis Shampoo versus market leader Pantene.
Notice how the difference is all on the right side - they make the most sales by far in the non-advocates, the one-time buyers. The Advocates on the right side barely make a dent at all. The argument, therefore, is to focus on gaining many, many more new customers and worry less about the advocates.
What those slides are missing is the reason WHY all those one-time users choose their product and services. It is likely because someone else mentioned it or recommended it. And those recommenders are composed of brand advocates. So, shoot for lots of new customers, but make it easy for the people who love your brand to help you do it.