I'm not qualified to comment on legal issues and contracts. In the case of EULAs, my understanding is that no contract where you surrender fundamental rights is

I'm not qualified to comment on legal issues and contracts. In the case of EULAs, my understanding is that no contract where you surrender fundamental rights is valid or enforceable. But even then, I'd want a lawyers advice before assuming it. And, of course, that's a good argument for reading EULAs very carefully. I've learned over several decades that any simple pronouncement that "X is ethical/unethical" is an effective way of ensuring that you will be wrong about some particular case. Yes, I think there might be cases where it is justified, but it would be very rare and require extremely careful monitoring and review. Two areas where it might come up would be medical research and research on children or adults of diminished capacity. In the former, there might be situations where the value of the research to the collective health and safety of the entire community would be sufficient to balance the use of such deception. In the latter, it may not be possible for your subjects to give informed consent (side note: this is, of course, also a ethical problem in experimentation on animals). The ethical dimensions of parents or guardians consenting to experimentation on their charges is extremely complex. I will go out on a short limb and assert that ethical experimentation using that sort of deception depends a great deal on the details of a given case. Very subtle changes in the experimental protocol could easily change its ethical acceptability. P.S: And, of course, there are a vast number of things that are completely legal but absolutely unethical.