So "it's" vs. "its" is yet another johnny-come-lately arbitrary rule without historical basis. Yay, one less thing to get annoyed by.
While talking about the English language, does anyone know what happened to thou/thee/thy/thine/ye?
Quoting from Wikipedia (http://en.wikipedia.org/wiki/Thou):
"Following a process found in other Indo-European languages, thou was later used to express intimacy, familiarity, or even disrespect, while another pronoun, you, the oblique/objective form of ye, was used for formal circumstances"
It's a vestige of how the Thorne transformed over the years - eventually it looked very similar a Y with a small "e" above it... leading to someone looking at an old document to assume it was just a Y.
We could be talking about two separate uses of the word though....
The same way in a short period of time words like "cool", "wicked", "fab. [abbrv.]" can rise and fall in cultural popularity, so can words like "thou" and "you".