I'm not sure what to tell you. If you sign up to work at Google or latest catpicture sharing startup, as a fulltime employee, you will certainly sign an 'Assignment of Inventions' agreement. It's completely routine and will not rob you of your precious inventions.
I don't see anyone arguing that there wont be IP related clauses. What I see people taking issue with is the idea that the extremely restrictive example given by the poster is "standard".
I've given you a counter-example. I worked for a venture funded Silicon Valley startup. I didn't sign anything that gave them rights to anything created outside working hours on my own equipment. Neither did anyone else there.
I don't doubt it is common, but I've also not seen anything to indicate that it's something you'll meet often enough that I'd consider it "standard". Maybe my company was the one single exception in the entire US, but that seems unlikely to me, especially given the other comments here.
