This does not mean the web does not allow for documents to be removed or deprecated. Content managers should avoid, when possible, simply removing resources, and should consider instead the correct standard procedure, which is to use the 410 gone status code ([RFC2616] section 10.4.11).
Whereas the 404 Not found status code only means that the server is unable to find the resource, the 410 gone status code means that the resource is intentionally unavailable. For the sake of semantics and caching (a 410 gone is cacheable unless indicated otherwise).
How many of you have actually gone as far as micro-managing your 404s vs 410s?
I return 410's for content that is really gone. I've seen absolutely zero side effects or changes in search engine behavior because of this. I imagine they'll continue to pound on the 410 URIs until all the inbound links are gone.