We generally use an UnsupportedOperationException to denote a scenario which is...uh...unsupported. This might be in a 'fake' ActionScript abstract class (ActionScript doesn't have a special support for abstract classes) or in a specific case where it doesn't make sense to support the operation. Sometimes, however, you want to support a particular case - just not right now. That's where ProgrammerTooLazyException comes in - it clearly marks in code why you didn't support the operation and gives you the added benefit of making sure these cases get implemented before code goes into production. My one concern would be that perhaps we're encouraging folks to refer to themselves as lazy, but hey, lazy instantiation is lazy, and we like that.