I loved the post on 37 Signals about throwing out your bad shots. Many people struggle with not posting every photograph they take -- look at facebook to see copies of similar, but equally crappy, shots in your friends' albums. In reality, looking back half-objectively, you could have left out a ton of cruft and still given a great overview of your trips and fun times.
I've been as guilty as everyone else.
I am getting a little better (only posted 8 shots from about 50 I took while on the boat wakeboarding), but I still have a long ways to go. I still keep every single shot on my hard drive -- even those solid black ones -- perhaps hoping someday I’ll get ahold of some forensic tools and dig out a gem inside there (enhance... enhance... enhance). In reality, I hardly look at even the top 5 pics from any photoshoot from more than a year ago.
Delete can be a tough button to press, but it shouldn't be.
When you're looking at code and you know some of it isn't used -- or maybe it's even commented out -- don't be a afraid to let go of it. We have version control so that you can always get it back.