I'd be curious to know why they wouldn't hold up—did your professor give a reason or mention any particular cases that led him/her to reach this conclusion?

In my experience (lawyer in Palo Alto for 7 years), parties can agree by contract to do or not do many many things. Even provisions that limit legal recourse, like the much-decried mandatory arbitration clauses [1] have held up all the way to the US Supreme Court. I would be very interested to know what legal basis there would be to invalidate a license agreement that says: you can have access to this content but only if you promise not to tell other people about it.

1: http://www.nytimes.com/2015/11/01/business/dealbook/arbitrat...

"parties can agree", but I turned on my TV after the legalese was broadcast. The average website or software shrinkwrap has a lot better contract formation than that.

That seems like a cop-out avoiding the issue. If you did see it, what's the argument for it to be unenforceable? Note that it should be unenforceable, but it's a hard case to make without a certain amount of "I know it when I see it".

And "there are no limits to the content of contracts people freely enter" is obviously an untenable position – we'd all agree that a provision giving me your kidneys, hidden somewhere deep in the ToS is unenforceable.

Yeah, interestingly they show it at the end (I'm sure there's a reason, but of course you could have turned it off before that pops up). It's probably also in the mlb.tv subscription agreement, which again doesn't make it necessarily enforceable, but if they also show it during the broadcast it makes it a bit more likely to be enforced than if it's just one of a thousand things in the clickwrap.