Apparently there have been a lot of law suits with Pixabay as well. I don't know how common it is in reality and suspect I may feel overly panicked, but it's so hard to tell. The communications with the legal team are shown on the site below. But the fact that apart from UK Government being sued on a different issue for using Unsplash, there aren't a glut of them coming up.
Most of the breaches I found when searching for CC law suits were more Flikr and Wiki over the licensing details not being honoured. But in this communication, Unsplash admit that a lot of the images on their site were uploaded without the knowledge or permission of the copyright owners! 😳
I don't know if I'll change all mine. It's a big job and I don't have suitable alternatives for everything. Will review things in dribs and drabs. Annoying to find this out after publishing 350ish stories though. And wonder if I'm over-reacting.
