I usually unfriend people during my annual FB spring cleaning only. The people who go are the ones who go are the ones I don't care much for, have abandoned FB, annoying kids, or people I don't recognize/don't remember adding (legit reason, no?).
If they're people I know and want to keep but they're being annoying:
- Hide their updates from my feed if they're posting annoying crap.
- Add them to the "restricted list" if they're being too stalkerish, with their likes and prying comments (i.e. lots of family members). The nice thing about this list is that it restricts them your "public" updates/photos only. Blocking them from only your basic posts/photo updates, but your likes and events' activity from showing up on their feed.