Being hammered by Splogs - anti-splog installed

hi,
any help, ideas welcomed.

I've recently deactivated the "invite code" function on my WPMU site (2 days ago) and now are being hammered by splogs - aprox 1 every 30 minutes

I originally was thinking the anti-splog plugin was working perfectly as I have never seen a splog in the past. current site has been published from very early versions of WP multisite / buddtpress/ from a couple of years ago and maintained upgrades etc.

it has only been in the last 6 months I implemented the invite codes for various reasons.

the only other possible factor is I have also disabled email verification (a function I require) about the same time invite codes was activated.

my thinking: invite codes was a sure thing against splogging even with email verification deactivated.
now that invite codes is deactivated I'm being hammered

also I do have recaptcha on, TOS activated, even during this post I just received my first spam comment on a blog site (not the main WPMU site)

question: is it possible that email verification being deactivated a possible cause?
I have noticed most of the splogs are not being acknowledged by anti-splog
But I believe the plugin is working at some level as 4 or 5 splogs are noted and marked.

anyhow any thoughts or direction would be greatly apprieated.
cheers,
Steve