I believe both are applicable, but the 404 gives me more flexibility in saying 'for some reason the requested resource is not available at this time...' and can be delivered on a number of 'bad' requests. (Just my opinion and reason for use.)
When I look at 302 threads closely I see Google (and other SEs) had to make adjustments to handle mis-use of, or mis-understood use of redirects and document requests (basic temp v. perm 'status codes') provided by many webmasters and hosts.
What I mostly see is webmasters not understand when Google follows the standard on a members website and when following the standard does not achieve the desired result of the webmaster.
I like the fact that SEs are helping people (and/or hosts) who do not have the ability to address these issues, by adding flexibility into the handling of certain requests, but think using the proper identification of (or at least communicating temp. OR perm. status of move, missing, etc.) resources when possible makes things more stable for webmasters and SEs.
Will 302s on a site hurt? I don't know. I know I have recently, successfully used 307s.
ADDED X 2: My desired result is the 2nd to last sentence of jdMorgan second post in the same thread... I would like SEs to continue requesting the resource.