Sorry that I missed this response! You want to find a server header checker tool (doing a Google search on those keywords will get you several such tools) and then put your 404 page into that tool. That will tell you if that page is truly serving up a 404.

That is certainly an interesting way of asking for a removal, but I could see a potential for it backfiring as well -- having people talk about your client having an infected site, for example.

I suggest reading how Ryan Kent dealt with removing links, and keeping very detailed records of the attempts to remove links, and his ability to get part of the penalty lifted in this Q&A at http://www.seomoz.org/q/does-anyone-have-any-suggestions-on-removing-spammy-links

Wow! I just have to give an expanded thanks (we don't have much room in the Endorsement area) for this detailed response. It's great to get some solid information about what it took to get a partial lifting of this penalty. It's certainly one I'll be sending other people to as an example of what to do.

For SEOmoz, I know some of our most popular (in terms of thumbs and comments) posts have been well over 2000 words. Adam, I don't have that post. What I do have is a roundup of 2011 posts by likes, tweets, etc. and you can look at those individually and see length (http://www.seomoz.org/blog/the-best-of-2011-posts-people-who-rocked-our-world).

I'd look more, but I've got a backlog of other Q&A questions due to being on the road. Driving from SF to Seattle today and tomorrow. Halfway there, and way behind on email and Q&A.