It's funny. I think of anonymity as something that has been part of the Internet going back through at least the last three decades of my experience with it. Back in the day you had anonymous retailers, let alone people using pseudonyms. It was very much part of the fabric. If anything, it feels like anonymity on the Internet is harder to achieve these days.
Even if you know the identity of a contributor, you have to consider the possibility that they or their systems have been compromised. I agree it's stressful and difficult to be constantly vigilant about contributions, but it's kind of all there is.