We're not all about being greedy capitalist pigs over at WPMUDEV ;) and here's something to prove it, goddamnit.
We give you, ahem, the catchily titled Signup Security Question.
It's pretty simple really, say goodbye to auto-registering splogs by asking a simple question as part of your signup process.
And what makes it extra funky is that it's 'powered by humans' - i.e. you change the question every week or so, and the sploggers aren't going to be bothered to keep up with you.
Well, that's the theory.
Have a go, whack it in mu-plugins, change the question in Site Admin and let us know.
(BTW it doesn't appear the first time you view the signup page, just refresh).