Which should all that needs to be written on the subject. It's something I've griped about before and doubtless will again.
But with three bites from the bad communication bug currently smarting, it's probably a good idea to give concrete anecdotes so that people who think that merely putting smart people together will get a product out the door.
1.) The DLL code freshly checked out from source control doesn't compile. Why? Because no one documented that some class files are obsolete and I should have removed them from my project setup. Everybody normally on that project "just knows that," you understand. I think it wasted more of the project alpha's time straightening that out for me than it would if he had just purged the files from the repository. The irony is that my "fix" was involved four lines of code.
2.) Three of the Office Illuminati are tough to catch off the phone or out of meetings, even just one-on-one. Now imagine that to get an idea of what the "bug" in the issue tracker even was about--not to mention trivia such as what system features it actually affected--you need info. from all of them. And before you can get that info., they need to talk to each other. Funny how that bug's still on hold as I write. And you'd better believe I'm making my disgruntlement known by dinging the billing number for the wasted runaround time.
3.) Part of a fix that it was my job to promote today involved deleting a folder. Were I not paranoid enough to ask for clarification, I would have whacked a client's custom programming work. In production. It turns out that the person who wrote the promotion instructions was referring to test data on a different server altogether.
Understand that I consider myself undeservedly lucky to work with people who are both smart and good. So it baffles me that there's so much assumption of mind-reading, when that's been proven to be false over and over again. We have a wiki, blogs served from the wiki, internal web pages, whiteboards, two source control packages, a highly customized bug-tracking system, and of course email, telephones and scratch paper for "call me when you're back from lunch" notes. Lack of communication technology is not the problem.
Here's the thing: You don't have to assume that your co-workers are stupid when you document things; you just have to assume that they are (very temporarily) ignorant. And the kicker is that well-written instructions can take less typing than poorly-written ones.