Where did all these cute photos of cats sleeping in boxes come from?

My recent run-in with the copyright cops got me thinking about photos on the Internet.
Whenever I use a photo that isn’t mine I try to provide a link back to the source. But many websites do not provide credit for the photos they use. I believe my use of photos from other sources is fair use because I’m commenting on the websites where they come from and I'm adding to the public discourse on media and culture. Plus, my blog is a non-profit enterprise.
But because other people don’t provide proper credit for digital photos and artwork, their origins and back stories get lost in the process. I’d like to know when and where many online photos were taken and more details about what they show.
My mother often forwards e-mails from friends with cute or interesting series of photos.
Just the other day she sent me a gallery of 25 photos of cats sleeping in small boxes.
I searched online to see if I could find the origins of the photos. I found two websites that posted the same photos without attribution: Damn Cool Pics and WireSmash.
Then I stumbled on a website that looks like it originally compiled the cat photo gallery in question. My Smelly posted the 25 photos and provided credit to all the photographers and links to the original source material. Most of the photos came from the photo sharing site Flickr, owned by Yahoo. Others were posted to My Smelly, a "social petworking community."
Shame on Damn Cool Pics and WireSmash for not including the attribution and source material. It’s not hard.

Photos: Cats sleeping in cardboard boxes (top to bottom) by Woodenship, Taurussun and Simplybecka on Flickr. Selections from a photo set curated by My Smelly.