One of the major problems that I have noticed with grammar, is the use of texting. Once people become comfortable with the use of the truncated and chopped words and slang terms used in texting, it seems to be hard for them to be able to form correct sentences and words in actual writings.
To me there just appears to be too much use of improper and illegally combined words, such at the "disinvited" previously mentioned. I will grant you that I am from an older generation that did not use texting, we did typing, not keyboarding; and we learned to write longhand, not print what we wrote. We had classes in English grammar and I have also studied grammar in ohter languages where it is more structured and controlled.
The proper use of a longuage is a beautiful thing, but to see it butchered, and made into useless words lis "dis", as in "to dis someone", almost makes me ashamed of the individuals total lack of intelligence.