I'd never seen the point of the fan view in the past, but seeing it now I think it could be useful for DNA, as it can highlight the ancestral lines that I share with a particular cousin.
We've never discussed Fan Trees, They're a nice visual look and you can see what areas you haven't completed, but do you use it to solve questions such as the one mentioned by Peter?
Below is a chart showing not only who I've found in my tree, but also the ones with crosses are my X-DNA inheritance path.

And below is my Y-DNA inheritance path

Can also show you by county
