I once instituted a personal rule: I wasn't allowed to bring anything new into my home — a gadget, article of clothing, book, etc. — unless I got rid of one existing item in the same category. I call it the One-In / One-Out Rule, and it's a great way to keep clutter in check. It means instead of having dozens of old t-shirts, of which I only wear five, I now only have a handful that I actually wear.
NOTHING COMES IN UNTIL SOMETHING GOES OUT
I think most organizations should implement a similar rule when it comes to their software, apps and Web sites: new features may only be added if an old one gets ditched. The feature used least often, or with the poorest utility, is the first one to go.
This kind of rigor not only forces periodic re-evaluation and re-prioritization, it reduces the potential for feature bloat and, thus, frustrated users.
But this isn't a hard-and-fast rule — there can always be exceptions. After all, you're crazy if you think I'm ever getting rid of my favorite-if-rarely-worn Big Lebowski shirt.