Edit: I'd like to go on record with a bet that by the end of the year, reddit will get more traffic than LinkedIn (which currently has a market cap in excess of $6,000,000,000).
Anyone want to bet against me?
The banner ad unit on the right of reddit is almost never running a real ad. It's always an ad for a subreddit or a pretty picture. That one single spot at $1 cpm at 2b pageviews could net reddit $2mm a month. That's a lot of money to be left on the table.
To put that in perspective, if Facebook were to get $1CPM they would be bringing in over $1B a month from just advertising. Facebook's revenue is about a third of that and doesn't all come from advertising (Facebook Credits and what not). It's even more bleak considering that Facebook has the ability to target advertising much better than reddit.
They can certainly make a bundle of cash, but it's a tough nut to crack.
I'm not sure I buy that. Reddit knows your interests due to your subreddit subscriptions, and if they wanted to scrape your comments they could easily find out a whole lot more. The fact that they don't is likely due more to their limited engineering team and a general distaste for that kind of invasiveness than due to its inherent difficulty.
Facebook doesn't need to 'extract' that information based on browsing information (although it probably could, given the number of sites that share information or use the fb api, and the links that users share with each other) and user posts (statuses, wall posts, notes).
Facebook has far more information available than reddit, so yes, it should be able to target ads much better.
If they can make money off ads, what makes you think reddit can't?
Here's a sample of why Reddit may be earning less than it should: http://www.reddit.com/r/programming/comments/mour1/4_books_f...
(disclaimer - that comment is on my own link and made me bitter unfortunately)
It's a ridiculous metric. Certain types of sites simply get large numbers of page views due to their nature and design.
Monthly uniques, repeat visits, and average time on site are a much more reasonable basis for comparing different types of sites (and even that is quite flawed).
Reddit doesn't really have anything like that. They may be able to monetize in other ways beyond advertising, but LinkedIn is already generating revenue well beyond ads.