I don't know how the sidebar ads work, but the featured links at the top of the page are run on a sort of auction system. Everybody that wants a piece pays howe

I don't know how the sidebar ads work, but the featured links at the top of the page are run on a sort of auction system. Everybody that wants a piece pays however much they want (minimum of $20) for the day, then all the ads are totaled up and each ad gets a percentage of pageviews corresponding to the their percentage paid on that days revenues. If that wasn't clear (and I'm not sure it was), assume you and I were both the only advertisers on reddit for a day. If I pay $20 and you pay $20, we would both have our ads displayed on 50% of pageviews for that day. If instead I paid $80 and you still only paid $20, then I would get 80% of pageviews to your 20%, regardless of the total pageviews for the day.