We try and keep on top of spam, but since it can happen at any time it is always helpful for forum members to report spam when you see it. If you are subscribed to a thread where the spam hits, I could imagine getting an email for that.
As already mentioned, it is a delicate balancing act to try and stop spam without preventing new members to jump into discussions. There are some restrictions in place on many areas... but if we restricted new users from posts entirely (which would be the only way to 100% fight spam) then we would be discouraging new members.
I think we do a pretty good job of catching spam as soon as it is reported, and many times we are already catching and removing posts as the reports are coming in.