Rules are for grammatarians--the speaking rules are for the many, many millions of other Americans.
That's between you and I.
We often bemoan the educational system in this country and the resultant "dumbing down" of our nation's youth. How on one hand can we be critical of our schools, then in the same breath, not attempt to incorporate of our own education into our day to day life. If we do not use and demonstrate those thing that we were fortunate enough to be taught, where do we have the right to condemn those that were not so fortunate?
Do we now through out the grammatical rules for the ease of expediency? I would hope not.
I have experienced receiving letters from young college graduates seeking employment. Many of these letters weren't written on a junior high school level. Perhaps these graduates were short changed by their teachers and professors or thought that grammar was simply a waste of their time. Young men and women with the benefit and privilege of receiving a college education and they are still unable to communicate using the written word. Pathetic.
I believe that if civilization and culture is to endure, it will only do so by way of pen and paper. To rely on verbal communication is grossly inefficient and haphazard.
I am not a grammatarian, only someone who recognizes the benefit that proper grammer lends to the ability to communicate accurately.
Not only does that sentence violate the grammarian's rule of using the object pronoun form after a preposition, but it also violates my general rule against ending a sentence with "I". To be sure, I'm somewhat flexible on that rule, but only to the extent that its violation is compelled by other rules.
BTW, one point I think 18th-century grammarians may have missed is that linguistic usage is often governed by prosody. Written language is derived from spoken language, and in spoken language constructs which are difficult to say are generally inferior to those which are easier.