The point of using an aggregator is that they supply MORE information surrounding your topic that the original source might. The original article or video might be great, but has no surrounding contextually relevant information that might also be useful or helpful. I personally love using sites that aggregate information for me about my hobbies, whether it be games or sports. I find more about what is going on because that site has done the "value added" work of finding and organizing it for me. Saves me time, because there are millions of sites out there that might have great original content, but I will never find them for many reasons. Not the least of which their SEO might stink. So thank you to aggregators whose SEO chops are good!
I have to second Niko's position here. Our main business model is "adding value through aggregation". We provide users in many markets aggregated content from a variety of publicly available sources on specific topics. While much of the content on our sites is technically "duplicate", so is much of the content on the NY Times. They syndicate content from the AP, as do many news sites. We do the same, and always take care to credit the authors and provide valuable links back to the original content source. Does this algorithmic change affect sites like ours?