I want to create a "social search engine" website. The idea is for people to search for jobs (or articles, or recipes -- I am necessarily targeting jobs), and be able to view them on my site, comment on them, vote on them, share them, etc. An example of this kind of idea is http://www.yummly.com which targets recipes.
My problem is with the copyright. Do I need to get permission from every site I want to crawl to display their content on my own site -- even if I am linking back to them as the source? If so, how would I go about this?
Also, are there any good ways I can have the social features while still being treated as merely a search engine? (As opposed to "stealing" content.)