I nearly turned down my current job because they were using a default contract that had clauses like that in it. It also said that they have control over everything on my computer, despite the fact that the laptop I bring in for work is my own personal laptop.

I ended up spending about an hour with their lawyer reviewing and amending the contract until those kinds of clauses were completely taken out. Lucky the lawyer was very amenable to the changes.

Always read the fine print, and don't sign anything if you're at all uncomfortable with it.