SevenCubed - 4:01 pm on Nov 14, 2013 (gmt 0)
Engine's comments just reminded me of something else concerning sourcing images from Flickr. I've noticed in some instances that the media owner will have applied 2 types of licensing to their works.
I've seen instances where a Creative Commons License is applied while simultaneously making the images available for commercial licensing via Getty. Now that obviously has a potential problem brewing knowing that for Getty < insert your own descriptive word here, begins with 'e' > is a business practice. I'd steer away from those.
Where should we include an acknowledgment?
Where ever. It doesn't need to be in a prominent position and a smaller font is what I use. Just something discrete. Page footers are usually a good place and in a font colour with less contrast to the background -- not to point of making it nearly invisible. Just mush it up enough to have it there without necessarily needing to bring attention to it other than for those who are specifically looking for it.