I clean out my friends lists all the time. No matter what site I'm on (with the exception of Facebook). If someone doesn't talk to me for an extended period of time, I typically end up blocking them for a while so they notice that I'm not appearing online anymore, then unblock them for a few days, then if they don't hit me up with an IM of any kind; even if it's a simple hello, I end up blocking them and deleting them from my friends list forever.
On sites, however, I just end up deleting the person without any warning that I'm going to be doing so. If they really cared, anyway, they'd find a way to find out if I deleted them or not. You know? What's the sense on having someone as your friend unless you talk to them?
(On PC, I remove them from my friends list, but keep them as contacts so they still have access to my complete profile just in case they want to start our relationship again)