The spammers have already fought back. Apparently Lycos' web page for this was hacked (and since repaired).
Personally, I despise spam. Love the meat product, hate the mail. On my work email, I get around 200 emails a day, more or less. About half come from an email list I belong to, and where I've had perhaps six spams in the past four years. Of the remaining hundred or so that show up in my inbox, about 75% are spam. It's pathetic.
One thing to consider if using this screen saver... they get your IP, too.
And on the thought... I believe it's wrong to do this. Sure, spammers are nasty, but does that justify creating a denial-of-service attack on them? Once they're done (if they ever are), how long until some other group gets focus, and this is launched on them?
*steps gingerly*
Would it really take a lot of anti-gaming people to decide that a forum like IW encourages gaming (that known bad behavior) and therefore want to launch a DDOS attack to stop this bad behavior? 'Tis no different than doing the same thing to spammers...