At the end of 2019, I made a case for online trees being a valid source, although with some caveats. I recently thought about a similar case for Pinterest, but the situation is not the same there so I wanted to dig over the main issues.
Like many people, I started a Pinterest account when it first appeared, and then got disinterested when I realised that it was all smoke and mirrors (or images thereof), that my feed could not be tailored to deliver what I really wanted to see, and when I got deluged by unwanted advertising. In fact, I have just closed my account as it had no value for me.
Pinterest has been criticised for many reasons, including some content being pornographic or obscene, being overtly political, hosting commercial scams, spreading misinformation (especially medical), or focusing on people's eating disorders or weight problems. But what was it supposed to be?
According to Wikipedia, Pinterest is an "American image sharing and social media service designed to enable saving and discovery of information ... and ideas", but the reality is much more mundane. It is now basically an image sharing site with no obvious purpose. You see images were supposed to be just a taster that encouraged people to pin them, and click on them to get information; an image on its own — with no caption, link, or accompanying information — is a dead-end.
Let me pick a specific case, one that initially encouraged me to look at Pinterest: images of old places. I love to see historical pictures of my home town, but on Pinterest they invariably contain no details, or any caption. If I wanted to search for an image of a particular place then I cannot — the search bar simply finds boards of that name shared by other users. If I happen upon a rare or interesting image there then I might, if I'm lucky, recognise the place, but what about the date, or the photographer, or the story behind the picture?
If I was doing this as part of a research project then I have a deeper problem: provenance. Where did the image come from? Who took the original, and is it in copyright? Pinterest does have a mechanism for a copyright holder to get material taken down, but this is fighting against the tide because it already makes it so easy for people to share anything and everything that they might find, online or otherwise. At the very least, it should have implemented a mechanism identifying the initial point of entry of an image onto Pinterest, i.e. who first loaded it, and where from.
The situation is more complicated than this, though, and doomed to failure in the hands of people who treat it like stamp collecting. I have several images in my blog posts that I have taken pains to get permission to display from the copyright holders, and I had shared those same posts via Pinterest using those images. And yet I have these images in isolation on other people's Pinterest boards. That is, pinned images, divorced from my blog, without the associated information, and without any provenance or attribution. The images had been appropriated to sit in someone's "gallery" of images that they like, but that serves no purpose beyond the private pleasure of such hoarders.
So, if Google turns up some image during your research that resides on Pinterest, what do you do? Would there be any point in citing it at all, in the way you might for other social media? Google does provide a search-by-image mechanism through which you might be able to identify a non-Pinterest copy — ideally being older and with more details — but then a Google search could equally have found that, so what purpose does Pinterest serve? As a means of sharing, it is naively structured and simply exacerbates sharing issues already present on the Internet. But as a source of information that is worth reading and citing then it is a non-starter.