The problem is any site that decides to grab this data gets an advantage over any site that does not, and the regular users simply don't care enough. About fou

The problem is any site that decides to grab this data gets an advantage over any site that does not, and the regular users simply don't care enough. About four years ago, a new trend just started emerging. Sites would ask user's for their Gmail passwords and scrape all the users' contacts to invite them for their service. I remember this because I was at a company where I refused to implement a service that requested a user to enter their Gmail password. They got someone else to do it. The issue was that we had competitors using this tactic and they were gaining a lot of users. Unless you have a way to level the playing field, you'll end up just punishing the ethical companies.