There's an epidemic happening and it must be stopped. I call it the Alone-in-the-World (AITW) syndrome. The main symptom is the inability to understand that one's actions affect others. For example, have you ever been in a slow-moving lane of traffic only to discover the reason for the delay is that nine cars up, someone is cruising along at a barely detectible speed, cell phone up to his ear, blissfully unaware of the chaos in his wake? He's got AITW.
Or how about the woman at the grocery store who has her cart strategically poised at an angle where no one can get by while she makes up her mind which brand of artichoke hearts she wants? Yep, AITW.
AITW is bad enough in those settings, but it's really bad in the workplace. Things get a little trickier, and more is at stake, when you're working with those diseased with the AITW bug. Successful projects depend on successful communication. So when you have people running around making changes in a plan without telling everyone whom change affects, you have a recipe for disaster.
For example, if you make a change to the interface of a tool the end-users in your company use, it would make sense to let them know. Seems like common sense, but I've seen that communication breakdown many times.
Also, if you make a change to anything that affects the customers of your company, you should probably let your CSRs know. Nothing quite rankles when you're a customer's connection to the company than having to say to that customer, "I wasn't aware of that change."
Maybe the problem is that no one knows when to classify a change as a "project." If it's a project, the project manager, ideally, will pass the word on. But if it's too small to be considered a project what happens? My guess is that programmers do what they're asked and assume the word will trickle down to the end-users and customers the same way the request trickled in to them. But that's an assumption that probably shouldn't be made.