There is some demo code at work that's been around for around 10 months, and I've added various features to it from time to time. Also, from time to time, the deployed code has to be put in a "known state" to actually do the demos. A month or two ago, some other guy added a feature, which makes the user interface fancier, so his changes need to be in all the demos, but he never checked anything into source control. Since then, I've added some features, all of them checked in. So now when there is a demo, this guy has to merge my changes into his code and then deploy it on the demo system. Except that what has actually happened is that they go back to the code that he originally deployed over 3 months ago, which doesn't have any the features I've added, which include changes that make the platform more robust. I can't deploy the demo including his features because I don't have his code.

One of these days, I'm going to ask him why he doesn't check his crap in.

I don't understand how some people can work on stuff while rarely interacting source control. I update my source trees often. I update before starting work. I merge in changes periodically during work. I merge in changes when I'm ready to check stuff in. I check stuff in when I'm done working on it.