Meh, if your job is to regularly create IP, it becomes difficult to prove what you came up with at home vs at work. And really it doesn't matter because you are usually paid a handsome sum for your inventiveness. I can understand such clauses as I change my risky situation of not coming up with anything of value and not having money for a steady wage but no chance at extreme richness. I am always free to stop working at my employer and try to score golden patents on my own...
I don't think the vast majority of programmers are paid to generate tons of IP.
More importantly, we're almost always only paid to generate IP in a single domain. So if I go home and generate IP for a totally different domain, there's no reason why my employer should have any claim to it.
But many companies will have it in your contract that they own it, regardless of relevance to the company.
