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It is tricky. As Michael said it is important to get your content indexed first, which can help identify you as the source. Google doesn't always do a great job of that. Generally, I don't worry too much about Case 1, but in your case, it can be tougher. The problem is that many download sites can have very high authority and could start outranking you for these product descriptions. If that happens, it's unlikely you'd be penalized, but you could be filtered out or knocked down the rankings, which might feel like a penalty. Here's the thing, with Case 1, though. If these download sites are simply outranking you, but you're distributing product, is it so awful? I think you have to look at the trade-off through the lens of your broader business goals. Case 2 is tougher, since there's not a lot you can do about it, short of DMCA takedowns. You've got to hope Google sorts it out. Again, getting in front of it and getting your content in the index quickly is critical. If you were hit by Panda, I'd take a hard look at anything on your own site that could be harming you. Are you spinning out variations of your own content? Are you creating potentially duplicate URLs? Are you indexing a ton of paginated content (internal searches, for example). You may find that the external duplicates are only part of your Panda problem - if you can clean up what you control, you'll be much better off. I have an extensive duplicate content write-up here: http://moz.com/blog/duplicate-content-in-a-post-panda-world