deep seated vs deep seeded – The first one is correct. A feeling or attitude is seated deep within you. No gardening is involved.
faze vs phase – Two completely different words! I know, right? Don’t let it faze you.
cache vs cachet – Having a hidden cache [sounds like cash] of cash might give you a little cachet [sounds like cash-ay].
stage left vs house/camera left – Stage left is left from the point of view of the stage, house or camera left is left from the point of view of the house or camera. I haven’t heard ANYONE use these correctly in AT LEAST the last year, no exaggeration.
prodigal – The prodigal son wasn’t prodigal because he came back. His behavior before he returned was prodigal. It has nothing to do with returning.
Raveling Out 
Are these student (as in university student) mistakes?
Sadly, they are peer mistakes. (Fellow bloggers and colleagues.) Since I can’t be this rude to people in person or in the comments sections of their blogs, I reserve the rudeness for here.
Some of those should be blindingly obvious though, shouldn’t they? Especially the prodigal son – ‘the prodigal son returns’ is the standard phrase, is it not?
Right! I think it’s the phrase that confuses people, though — like maybe he was prodigal because he returned? And it’s a redundant/tautological phrase? I don’t even know sometimes.
It seems that they don’t make the connection between the verbal and the written. I mean, verbally it’s obvious…apparently when written it is not so.
Thanks for pointing out the faze/phase. I have such a difficult time convincing people that faze is a word.
J- Good point. It probably has a lot do do with that. When I was a kid, I read so much that I knew lots of words in writing, but ad no idea how to say them. I bet everyone has that disconnection on some level.
R – I know! I think if people haven’t seen that one written down, they think “faze” is just some bad spelling a la text messaging or the lolcats.