I think of the biggest problems with anonymous apps is the lack of reputation / consequences. I have always believed that anyone can be an absolute troll or a bully or whatever when presented with the right circumstances. Those circumstances tend to apply to far more people when you advertise yourself as an anonymous app.
However anonymity comes in more than one form. It can be not tied to your government issued identity. Or your work identity. Or your Facebook identity. Or your party-all-night identity. It can mean your IP can't be tracked or your communications are fully encrypted to everyone except the person on the other end.
Reddit actually started relatively anonymous. People tended not to use usernames that they used elsewhere and were extremely careful about posting personal information that could be tied back to them. You didn't have to enter and email (and were never asked to actually - you had to dive to the bottom of your settings to be able to reset your password). But even so, add some magic Internet points and you cut down on the cyberbullying and trashiness. It also helped that reddit's initial user base was mostly older programming males, not middle school girls. Lurk moar applied and improper grammar wasn't accepted. You didn't live on your phone and you didn't reddit from your phone.
Hubski is very similar, although a lot of people who came from reddit use their reddit identities. Again, why does Hubski not become a breading ground for crazy middles-shoot hate? (1) Empowering individual users to be their own moderators (2) Inspiring thoughtful discussion by design...and by leading by example (3) a reputation system to encourage good behavior and a user-moderation system to discourage it.
I guess my point is...anonymous purely to be anonymous usually attracts the wrong user base which perpetuates a spiteful environment. There are steps you can take to mitigate that, especially in the early days. Giving anonymous middle schoolers the ability to say whatever and not moderating it is never going to end well. 😬 But giving users power and reputation and rules and providing value beyond anonymity has a better chance of thriving.