"The nation’s top auto safety regulator, the National Highway Traffic Safety Administration, said on Thursday that at least some Tesla customers who experienced suspension failures with Model S luxury cars were asked to sign confidentiality agreements about the issue."
http://www.nytimes.com/2016/06/10/business/tesla-model-s-nht...
The fact that they felt the need to tell NHTSA about it is proof that the agreement is a smart move on Tesla's part.
Most people would sign something like that over spending thousands of dollars for a repair. Just imagine it is the battery and they choice is like "well, you can pay $20000 yourself or sing this paper and we take care of it".
Again, it's your problem if you can't afford to not take the offer. You should be thankful that all you need to do is sign some kind of NDA.
What I find hilarious is that people sign the agreement to get the free repairs, then go ahead and complain about the agreement anyways. Well next time you need an expensive out-of-warranty repair, you're not getting a free pass :P