Google uses it internally every Friday at their TGIF to prioritize what questions Larry and Sergey should answer first (in addition to the ones asked in person). All week long people submit questions or concerns and Googlers vote on them to determine if they are relevant or not. It could be used for other things too though... really anything that needs ranking. Ideas could be ranked, or you could pose a question and have the answers ranked. I'm sure there are other novel uses as well. It's a pretty general system.