Yes, when it's truthful. When it will assist keep innocent people safe, and when you can be straightforward and face those you are snitching on. It is not your job to punish others anymore than it is someone else's job to protect you. If you have evidence that someone has done something wrong, then you should report it. There are agencies that can help you if you feel threatened or unsafe, such as the police or your parent/guardian. In conclusion, it is okay to snitch on someone if it is necessary for the protection of others or if you can be straightforward about it.