I want to know particulary about US.
When I say state, I mean state within the US. (California, Washington, etc.) Each state has their own labor laws. What may be enforceable in New York, may not be valid in California.
Those of us on this board are not lawyers. Before you enter into a contract such as this, you really should consult an expert.
Like I mentioned earlier, I would probably avoid a company that presented such a contract, but if the offer has other benefits and you are interested, contact a lawyer.
Wording on such contracts are always negotiable. You could strike or rewrite the offending text in the contract then return it to the company for approval. A good lawyer will help you with this.
Once both you and the company agree on the wording then you can sign on the dotted line.
I think most people don't realize that they can negotiate in these situations.