A couple weeks ago, Google has vastly improved their site move documentation, while also updating their mobile smartphone documentation.
Alistair Lattimore posted on Google+ asking why the documentation for smartphone guidelines specifically recommends using 302 redirects over 301 redirects? 301s have always been the recommended path for SEO purposes because they pass the best link equity from URL A to URL B.
But no, Google specifically wrote a 302 in the documentation on purpose:
I asked Maile Ohye and Matt Cutts of Google if this was indeed on purpose and Maile said it was 100% on purpose and not a mistake. Matt Cutts said the reason was because you may want to change it in the future and they didn't want it to be a permanent thing.
I should clarify, only use 302s when moving from the same URLs to separate URLs. Make sure you read the documentation carefully when going this route.
Forum discussion at Google+.