Any search engine has an image search service. Typically they make profits (with ads) offering images, they do not own and, since it is unlikely that images are in the public domain, they use generic disclaimers, such as "Images may be subject to copyright".
It should be noted that professional image sellers use, on their websites, sample images in low size/resolution with watermarks and they make available the high quality images only to paying users. So those scraped by search engines are the low quality images.
In a similar fashion, with respect to articles' images, Wikipedia states "it is believed that the use of low-resolution images [...] qualifies as fair use under the copyright law of the United States."
That being the case, what if, we do the same in a presentation for a talk? i.e. we enrich the presentation with a couple of images found, say, in images.google.com.
Is that still a fair use?
Can we too use a generic copyright disclaimer? Or Is it a good idea to add a reference to the image source at the end of the presentation?
It bears mentioning that the images in a presentation are only an embellishment to a larger work, while a search engine is selling as-is copyrighted images.