For anything...or...when might it be acceptable to say "I Don't Know..."
Always. More people should do it instead of making up a shit answer.
Yep. There are questions whose answer we will probably never know. Besides, depending on factors such as relevance and time/resource constraints, sometimes a question may simply not be worth, or even practically possible, to explore.
There are many questions ive been asked that i didnt know the answer to.
Yes. Unless one knows (or can figure out) absolutely everything, there are bound to be times when that's the only honest answer.
I don't know. Is it?
Yes, a true statement is much better than a false answer.
It is when being interrogated by law enforcement officers.
Better then lying
If said honestly, yes.
Ever? Of course!