Was learning to lead trad on a multi-pitch route, and didn't set up anchors correctly. I was belaying off myself (not the anchor), and had a ton of slack between myself and the anchor. The follower pulled out the last piece of pro and then fell. Since I had all this slack behind me, I went rolling down the rock until all the slack was out between myself and anchor. Luckily, follower was fine, but felt like absolute moron!!