So how does this all work?

We query the sites' content 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 Pinterest, where we scrape the data from their list of trending pins.

How often is this refreshed?

The images are updated hourly, and the videos are updated daily.

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.

Some of the Pinterest links seem like they were posted a while ago.

Yeah, but they just recently received a lot of repins.

I have a great suggestion for the site. Can I email you?