Thanks for your thoughts and suggestions. It is a major pain, isn't it?
Our spam blocker (affectionately [by me, just now] named Señor SpamBot) does snag most spam posts before we can get to them. Most of the time, when we come in on Monday morning, a good 90% of the spam has already been removed and the spammer has been banned as a spammer from our forums.
As for holding new posts until Andrew or I can look at them, I can definitely see the logic there. Unfortunately, with such a small staff, this would take up pretty much all of our time, since we get so many new sign-ups a day. And, most people who are newly registered and go on to post for the first time are not spam, so there's no need for us to monitor their first posting. And, as mentioned above, Señor SpamBot is doing a good job of catching spam before we even come into the office.
We don't think that this is a disgruntled tour member or another tour company going rogue and trying to take down our tour forum. We're just going through a bad patch of spammers right now. Their bots will go away eventually, especially if we keep being diligent about reporting and banning.
Thanks again for your patience and attention to these darned spammers!