Is it legal to use images from social networks for research? I would like to use images from social media (e.g. imgur, Facebook, Flickr etc) for research (ie not for profit or any industrial use).


Would it be legal to use images (for analysis, etc), if I do not store them locally?
Would it be legal to create a dataset of such images, that I will later publish with my future paper?
If it is not legal, how can there be these existing computer vision datasets of thousands (and even hundreds of thousands) of images taken from Google search or social networks? Surely the authors didn't ask every owner for permission.
In order to copy or redistribute images that you don't own, you have to comply with the terms of the license under which the owners have released the images.

Some images are released under licenses (such as Creative Commons licenses) that allow copying and redistribution under various conditions (e.g. attribution, non-commercial use only, etc.  - depending on the specific license.) 

For example, the People In Photo Albums dataset was "collected from Flickr photos
with creative commons licenses", according to the paper. Similarly, Yahoo! Labs compiled a dataset of One Hundred Million Creative Commons Flickr Images. And Google released an Open Images Dataset dataset of images that are listed as having Creative Commons licenses.

If there is no license accompanying the image or no blanket license applying to all images on the site, you have to assume that it is All Rights Reserved - in this case, you would not be able to redistribute these images.