You can set a stricter filter for new members and just approve posts that get sent to the spam filter wrongly.
Many forums also have a rule in place that a new member has to have a post in an intro thread and the intro thread post has to be approved before they can post anywhere else. I'm sure something like this could be implemented here, and with the sheer amount of mods we have it shouldn't be too hard to stay on top of. Easier than continually deleting spam, anyway.
What about people who are contributing but show up with advertising in their sig from their first post? I am not referring to people where making their own dog supplies, but say, including a food's tagline to all their posts.
Does that make us targeted more by advertisers if they are paid, and not banned?