I don't think it would be a good idea to implement a 1 day no post policy.
All that will happen is that they will post on the second day and will stop the legitimate users from posting on sign up.
Mike and Terry already have a good security system in place on IIS to limit spammer sign ups and whatever gets through the moderators pickup even before they post anything.
You don't get to see a lot of the spam posts, they don't last long on here.
What you see posted is the very few that slip through the 'net' on rare occasions while we're not online.
On these occasions the members report them and we get an email alert which we act on asap.