Me and my friends went to the mall

(Grammar Questions I Couldn't Answer)

I was correcting a piece of student writing when I came across "Me and my friends went to the mall", and was unsure of whether to mark it or not.

Technically it was a mistake, but it was a mistake that even native speakers would make.  (I've said similar sentences myself).  So I asked my manager for a second opinion, and he advised me not to mark it.

Of course, according to a descriptivist view of language, native speakers do not make mistakes by definition.

...and yet, it is an interesting use of language.  Our language faculty would never allow us to say "Me went to the mall" so why does it allow us to say "Me and my friends went to the mall."

I suppose one answer is that the addition of "and my friends" confuses our language faculty, and causes it to lose track of whether "I/me" is functioning as an object or subject.

But when you consider everything else that our language faculty effortlessly keeps track of, this explanation doesn't really make sense.

For example, the language faculty effortlessly keeps track of subject-verb agreement, even when the subject is separated from the verb by a lengthy clause.  (e.g  "The boy who I told you about last summer has a new dog.")
And our language faculty effortlessly keeps track of whether the relative pronoun is acting as a subject or object in a relative clause.  Every native speaker of English intuitively knows that a relative pronoun can be omitted if the relative clause is defining, and if the relative pronoun is functioning as the object of the clause.    And so every native speaker intuitively knows that "This man I like is tall" is acceptable, but both "the man likes me is tall" and "Thomas I like is tall" are ungrammatical.

So with all the complex operations our language faculty can keep track of, why does the addition of 3 little words "and my friends" suddenly cause our language faculty to forget whether to use the subject pronoun or the object pronoun?