I refuse to join Pinterest. They still steal our bandwidth from our servers to serve pictures from us by hotlinking them from my servers. That's where they have a browser on their servers, that come here acting like a visitor who clicks on the image here, but to display there, rather than save the image or catche the image to display there using their own server resources. They make millions of dollars. They should pay for their own resources, bandwidth, & servers, instead of sneaking around leaching off of poor & independent sites like ours.
They claim they don't do it, but I catch them regularly hotlinking to our pictures, stealing our bandwidth, & consuming our server resources. They're damn sneaking about it too. If I write some script to block them or block their ISP, they get in through disguised as another fake visitor, through another one of their ISPs or a new ISP ID range that I didn't block yet.
I used some script blocking to block their banners when I visit there, so I can see their pictures without their banner asking to join blocking my view, but sometimes it don't work when viewing their full size images. I suspect the ones it don't work on are also ones they're hotlinking to, & stealing somebody else's bandwidth to display.
Another very scary problem about them is, that if a picture or pictures from a particular site seem popular, they will spider the site to collect more images, & create a section titled after keywords found at that site... without the site owners or image owners permission. Then, Pinterest may copy the images over to its own servers, & their copy will still exist even if the site or image owner deletes the pictures.
The problem with this is, that Pinterest claims ownership & rights to of any and all images used on Pinterest web sites according to their terms of service.
So years later, they can turn around sue us, or issue a take down notice for us to remove the images by claiming they own the copyright to them. Anything posted on Pinterest by users, or anything posted by Pinterest by their spiders, or fake users that they created themselves, automatically becomes their property according to their terms of service. By posting at Pinterest you automatically signed away all rights to them for anything you post there when you joined. It's in the fine print of the agreement you made when joining.
They create a full-size image from your site, which you have no longer have control over, that will compete with your site's images in search engines, and perhaps, erode the traffic to (and value of) your web site.
Say someone links to an article or post you've made. Wonderful news! Now, interested parties who might never have found your site can be exposed to your material. But what if someone pins a photo from the "linked" post instead of your original? You guessed it. The person who linked your content gets the click back and not the original poster. Add to this the fact that Pinterest makes it incredibly easy to re-blog the Pin instead of the original content, and basically you've lost all control over ownership of your work.
Pinterest is not our friend. They will ruin or destroy small or independent sites, & take over their material for their short term profits. It doesn't matter to them if they destroy or exploit sites, because for every one they helped bring down or ruin, there will be another new one to exploit for a while.