Scott Barnes has an interesting entry about Evangelism.  In it he quotes Guy Kawasaki on his The Art of Evangelism - saying that "Look for agnostics, ignore atheists".

Firstly, I agree with this point entirely - but I feel it should be renamed to "Look for agnostics, ignore theists".  What Guy is really saying here is that if somebody already has a Tool/Product affiliation then it's hard to persuade them to use another tool instead.  Taking the religious analogy further - I would say that atheists do not believe in affiliation with a product or tool.  They have 'no belief'. 

To me, the analogy to religion is a little stretched.  Religious evangelicals try to persuade people into believing in something that there is no evidence.  They preach the use of faith.  Whereas, technology evangelists preach the merits of tools and products based on evidence - which is very different.  Who would adopt a technology based on blind faith?