Sometimes people forget that no idea is unique, and who cares if it's been done before? You're doing it differently and for a different audience. I'm a still-in-print journalist, and I see crap like that from people all the time.
My favorite recurring complaint is:
Q: "OMG why wasn't *IMPORTANT TOPIC* covered in the paper?!?!"
A: OMG it was on the front page. You just didn't read it.