Well Kate, standards of writing and speech have indeed gone South in the last decade or 3? Thanks to shows like the wretched Eastenders (etc) how often do you hear people say something like "myself and me sister would of gone down the shops . . ."? Etc etc, orright, innit?
People all too often get their, they're and there muddled up, and I presume that folk writing it's and its toss a coin to decide which to use, as all too often it's the incorrect version for that context wot gets put, innit?
Oh, and the BBC is a huge corporation, and most such entities employ some folk who make mistakes -- ever had a chat with something like British Gas lately?!