Well there is nothing illegal in that. I have seen ppl copying content and creating websites. If you can mix it up with something unique you'll get ranking as well. There is nothing in google TC saying RSS content blogs will be banned lol. Even I have seen websites with content from Digitalpoint threads. NEWS for you isnt it ?
well not illegal for adsense however Google may penelise your site in ranking or remove you from search for using other peoples content
I doubt it is illegal. It works similar to how RSS directories auto post newest RSS feeds. Unless you are somehow spamming the website or otherwise, it should be legal. The question is: what you using this site for that simply posts content from Amazon and Yahoo answers? Quick way to get high up in the SERPs? Fast way to build content?