I have always considered this, but never done it. If I was to prune 0-post count accounts I would also look to make sure they have not been online in more than a year at the very least. I would also ensure I have tried to communicate with them. If you've done both of those things and still feel like you must delete them I suppose go ahead!
I think this also depends on the niche of the forum though! Video game forums - you might not need any posts because maybe you're just wanting a more central place for all gaming news or finding people to add. Even on a niche like Admin Junkies - I can see users not having any posts and still lurking and perhaps using tools and tips to better their community.