Spambots are pretty easy to keep out of XenForo, but some spammers are not bots.Hello TheJason. From what I've been told, new members must reply to a challenge question, when registering. That does not prevent all automated registrations; it only slows their progress, as bots can prompt spammers to answer the question and then finish registering.
Were a spammer to register (by spelling 'htam' backwards) and then post spam, would you prefer to see their spam appear in the forum and be removed later versus deleting the spam (and its author) through manual moderation before it can appear in the forum?
My preference is to keep as much spam from appearing on the boards as possible. That requires manual moderation.