When I was in college, I was told never to use "firstly," "secondly," et cetera because they weren't words. Now, they've become words because people use them so much.
Same thing with people misusing the word infer- so many people don't understand what the word means or how to use it, it's commonly interchangeable with "imply" now.
I'm guessing that the current phenomenon of people saying "ur" because they cannot correctly use "your" and "you're" will become acceptable eventually as well. I used to think this was a bad thing, but now I'm not so sure. Years ago, French scholars decided that French would remain a pure language- today, fewer people speak French than ever before, while English is becoming the language of the world- the fact that it is such an elastic and malleable language is much of the reason.
Unless you're a republican, then the reason is CAUSE MERCANS SPEAK IT AND MERICA KICKS ASS FUCK YEAH