Of course you could, especially if you were using a lot of them over a long period of time. I have never dealt in Netflix accounts, however I would think that your risk would be that Netflix would take action against you rather then the account holder taking action against you.

The account holder likely couldn't care less about some random person using their Netflix account, but doing so will cost Netflix money and cause them problems with having to deal with increased support tickets in dealing with reset passwords, ect.