Anywhere someone is allowed to express their opinion. While we think of this as detrimental it's actually a key component of crowdsourcing. If you get enough people expressing their perspective you will generally come up with the best solution. But for that to happen you need a range of perspectives. Some negative, some neutral and some positive. Even the most ridiculous notion may have either have some merit or trigger some discussion that can lead to success. It's also a learning experience, no one ever learned by being 100% right all of the time. It's ok to fail, or to have a bad assumption. Too many people are afraid to speak up which is too bad because right or wrong the may contribute without knowing it.