Is there any situation in which disagreement between subject and verb is acceptable?
For example, I heard this song
... 'Cause it's late and your mama don't know ...
I think it's used in informal contexts. Am I right?
Is there any situation in which disagreement between subject and verb is acceptable?
For example, I heard this song
... 'Cause it's late and your mama don't know ...
I think it's used in informal contexts. Am I right?
It depends what you mean by acceptable. In certain cultures some people don't like to use correct grammar in case their friends mock them for it.
If you are talking about the English used in education, business and so on then you should use verbs correctly.
Note that even informal contexts differ. I would never say "your mama don't know" no matter how informal I was being. For other people it would be normal speech.
As you've already identified, it's acceptable in song lyrics, but you've to bare in mind the song's writer probably didn't give a hoot about subject-verb agreement; they're more concerned with what sounds good or fit the mold for the rhythm of that particular song. Change "don't" for "doesn't" in your example, and you'll see what I mean.
In any type type of writen prose, writing which is intended to communicate a message, it's not standard practise to misalign subjects and their finite verbs, except perhaps in direct speech when you're trying to convey the informality of a fictional character or a person being interviewed, etc.
That's my take on it, anyway.