In a recent meeting with the team I do things for they were upset that the new girl was doing things at exactly the speed I told them to expect; namely 3 days for the type of job in question. (Not Perl work but ActionScripting.)

They said many things along the lines of, "How can it take that long?"

I told them how and then I reminded them, pretty forcefully b/c I was tired to the point of being angry of being ignored on the issue, that this was not the first time they'd heard this information explicitly but the third in six months.

They said (real quote): "Well, that just doesn't scale."

I explained in further detail. File system complexity, new employee, CVS delays, no testing framework except live, Akamai cache needs to be cleared to even know if you're looking at the right files, one change means 4 hours of waiting and your team always requests multiple changes after the spec has been agreed on.

"Well, that just doesn't scale."

...and believe it when I tell you that it went around again and came back to: "Well, that just doesn't scale." From the same guy all three times!

Not all the people we work with or for are this dense and a-technical, but what I've seen isn't much better than all. Many of these people are completely unable and unwilling to understand or even listen actively.

adrianh has the technique for combatting the problem when it's only communication and not IQ in the way: get them to repeat a summary back to you verbally. You quickly find misinterpretations and things that have been unintentionally ignored.