While it can be put into a work contract, its never been in any contract of mine (I assume it is in contracts for union employees and for some executives). Many states do require that companies above a certain number of employees have to give notice, usually called WARN acts (and it looks like Oregon's requires 60 days notice according to https://www.oregon.gov/highered/institutions-programs/workfo...). Employees do need to pay out any unpaid holiday or sick time (which is why unlimited vacation is bad, since you don't get cashed out).

Normally when you get severance, it's in exchange for liability from lawsuits and to prevent bad press and sharing of trade secrets. What this does is make it much harder to sell Treehouse since there's now a fair amount of liability attached.