I have seen contracts that made the work I was meant to do for them impossible, that type of work wasn't allowed under the contract.
The classic example is a company wanting me to work on some open source software and potentially put in patches on it but having a clause in their contract that assigns all rights to the software I produce to them.
They don't often read them themselves to see if they are sensible or correct before sending them. The entire situation is really dumb, no one anywhere in the process seems to read them.
