While I agree with +Robin Good
that content curation is not content marketing, I think that content curation DONE RIGHT can be an important part of your content marketing strategy. What does "done right" mean?
1) Reading and understanding the content you are curating, as opposed to "keyword" scanning
2) Adding your own layer on top of the original content to create something new
3) Adjusting the original content to your target audience, providing a real value for them specifically. Highlight the parts relevant for them, use the content to start a discussion, etc.
In any case, content curation alone cannot be considered a content marketing strategy, you need to also create original content.