All Facebook users have agreed to be part of research experiments. It's in their ToS. If you got people to agree to allow you to enter their homes for research it wouldn't be unethical for you to do so.
ToS are a copout, and in my eyes a tragedy of the modern legislature around software services.
Every single company in the world knows very well that 99.99% of their userbase won't read the ToS, and use this to do whatever they want with their users' information and privacy.
There needs to be dramatic improvements in that area.
