Matt’s right, allowing anonymous comments is a terrible idea.
However, don’t force people to reveal information about themselves which isn’t relevant. Often that includes their name and most of their personal details. If you require a birthday for people to register, you're asking too much.
In the early days of online communities, nobody revealed any personal information and nicknames were standard. The relationships were stronger back then too. These worked because nicknames were repeatedly used and everyone could build a relationship with the person.
You don’t need people to reveal personal details about themselves for an online community to work. You just need people to use the same name throughout their time in your online community. If they change names without notice (or fail to use a name at all) nobody can have a relationship with that individual.
Don't allow anonymous comments, but don't demand irrelevant information. Let people reveal what they choose when they feel it's relevant.
