After I posted my recent car brand etymologies infographic, someone pointed out in a comment that I used the phrase based off instead of based on (which is considered correct). This mortified me; I normally don't make grammatical mistakes like that. However, as I looked around, I noticed that a lot of my friends, classmates, and random people on the internet were saying it. Intrigued, I did some research, and it seems like the new usage seems to be increasingly replacing the old one, and in a few decades it may be the norm - Google NGrams shows based off becoming very popular in the 1990s and Google Trends has shown that it has just continued to rise meteorically since then. Apparently, people are confusing their prepositions as the phrase becomes more and more dissociated from the concept of an argument being built on something and instead likened to expressions such as going off. Fascinating.
Update: a day after I wrote this, I attended a debate at the Harvard Institute of Politics where one of the speakers used the phrase. It's everywhere, and it's infectious.
Adam Aleksic, a freshman studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, and law.