Daniel Steinberg has been signing crummy contracts with traditional publishers for a long time, which apparently means he is no longer bothered by other crummy contracts he runs into:
I’ve been told by a publisher that they want a second edition of one of my books. Their conditions on me are that I drop this series of ebooks I’m working on because it might compete with the title. When I said no they responded that that’s ok they’ll just get someone else to revise my book.
My book.
It’s not really mine. Even though the copyright is in my name, that turns out not to mean very much.
So am I bothered by the iBooks Author EULA? No. But maybe that’s because I’ve been signing contracts with traditional publishers for so long.
Traditional publishers have standard contracts that are filled with all sorts of onerous clauses. One reason I have been represented by a tough-as-nails literary agent for 15+ years is so that crap like this doesn’t end up in contracts I sign.
That 15% commission seems like a lot until you run into situations like this, especially with a successful book.
Ed Bott (@ wordpress.com) 
That agent is tougher than nails. She is The Hammer!