So how does this all work?
For most of the sites we query the content on each site using their APIs, and select the most popular image or video. For example, for Reddit we combine the results which are currently on the front pages of all the most popular subreddits (e.g. pics, funny, aww, AdviceAnimals), extract all the posts that contain images, and then select the image with the greatest number of upvotes minus downvotes. For YouTube, we use the "most_popular" feed of the API v2.0. The other sites work similarly except for Imgur, where we scrape the data from the front page.
How often is this refreshed?
The images are updated about every hour, and the videos are updated daily.
Is there any way to see previous images?
You can use urls like www.oublio.com/shared.html?site=reddit&counter=720. One way to see the current value of the counter is to click the "share this image" email icon, and you'll see it in the link there.
Will you add Pinterest?
Yes, once their API allows this kind of query.
But that reddit image that you had up wasn't the highest ranked on reddit?
The other image was probably already on oublio or is coming up next.
I have a great suggestion for the site. Can I email you?