Grammar and basic execution of it are fluid over time. Part of my job these days is designing systems that can do useful things with online communication and wow.. trust me, you ain't seen nothing. Learned a lot about natural language doing these projects.
Now, having said that, we currently sit at the highest literacy rate we've experienced and the lack of formality in language is really nothing new. I love doing historical research and reading on various topics and you'd be really surprised at how awful grammar and spelling were in the past. English as we know it now has been through several standardization attempts (something the French still do actively) and it's the only reason we have any sort of nearly uniform conventions that we do.
The worst of those passes was back in the 1800's when grammarians decided that English needed to be more Latin like in grammar (cause Latin was perfect!). One side effect of that was my favorite ranting subject, the banning of the split infinitive. Since in Latin, an infinitive verb is just one word (as opposed to English's 2 word construct "to go"), the grammar police decided that it was improper to casually split an infinitive. Thankfully, that rule has been dropped by all but the most Procrustean grammar hawks or we'd never have had "To Boldly Go".
So, wait, what was I saying? Oh yeah, grammar.. informal language has always been atrocious. Look at the graffiti from Ancient Rome or Greece. (The Greeks had a word for grammar/vocab misuses - solecism. It came from them making fun of the dialect of a Greek colony) Look at the odd personal abbreviation and short cutting systems used by scribes copying ancient texts, etc. (Part of the reason translating ancient texts is problematic)
And then.. here in America, where being/displaying an education has always been viewed with a jaundiced eye by a majority of the population, you have people who deliberately avoid appearing too conversant with grammar rules to fit in. So, language.. it's a sticky wicket and always appears to quickly heading somewhere awful, but f##k it, it's a piss poor way to transmit ideas and the only one we have.
And why do I have a chihuahua sitting on my neck, this is awkward...