Google's John Mueller in a Google+ hangout this morning said at the 22:15 mark into the video that Google may decide that at some point, your 302 temporary redirects should be 301 permanent redirects.
He said there is often a lot of confusion around 302 redirects. He said they perfectly fine to use. 302s, just like 301s, pass PageRank and link signals. It is just that when a 302 redirect is set up, Google will initially show the originating URL in the search results, because Google thinks it is a temporary change. But as time goes on, it will think it is not temporary and then show the destination/target of the redirect in the search results - as they would with a 301 redirect immediately.
Here is the transcript:
I think there is a bit of a misconception out there on 302s being bad for your web sites and being bad for your PageRank... In face, it is definitely not the case.When we recognize a redirect and we see it is a 302, we assume it is a temporary redirect first and we assume you want the original URL indexed, not the redirected target. In general, that is one thing we like to do there.
However, when we recognize it is actually more like a permanent redirect and 302 is something that you may have accidentally set up, then we do treat that as a 301. We say, instead of indexing the redirected URL we redirection target.
So it is not a matter of passing PageRank or not, both of these redirects pass PageRank, it is just a matter of which of these URLs we actually show in the search results. Is it the one that is being redirected, which would make sense if it is a temporary redirect. Or is it the one that is it being redirected to, which would make sense if it is a permanent redirect.
We do look at the HTTP result if it is a 301 or 302, we also try to be smarter about that and try to fix any mistakes the webmaster might have made.
Here is the video embed:
Forum discussion at Google+.
