Anybody even remotely involved in designing anyth9ing connected to a network should watch Raph Koster's GDC talk about the ethical issues involved in developing AR and VR games. Except it's not really about "games" as we usually use the term. "Twitter" is a "virtual world"/MMO where they only bothered to built the chat feature.

This is really about the ethics and responsibilities that come with managing social spaces or infrastructure that people use to interact socially (which necessarily includes the problems that humans always have). The MMOs (and the MUDs/etc before 0them) have been working on these problems for decades. That doesn't mean they have the solution, but that experience does include a lot of lessons about what not to do; far too many projects are choosing to learn those lessons the hard way.

http://www.gdcvault.com/play/1024060/Still-Logged-In-What-AR