tedster - 11:00 pm on May 8, 2010 (gmt 0)
There's an added challenge when someone's infrastructure (especially their tracking and analytics) intentionally uses query strings. Yes, I know that it's not a good idea, but WebTrends has done this for a long time and that means some enterprise servers are stuck with it until they can do a massive redevelopment project.
In those cases, the site needs to strip the intended query strings and redirect them to the correect base URL -- and also deal with the spam attack. The easiest way out is often a 301 redirect to the base URL with a 200 OK, and then just accept the spammy link juice if Google actually sends it through. Even better is stripping only the ?WT=[campaign tracking] query string to resolve with a 200 and sending the other spammy query string versions to a 404.