[rchaud]

Facebook has best-in-class behavioral advertising tools, and can be used to create highly specific segments for ad targeting. You can sell pretty much anything on Facebook, so that attracts advertisers.

Reddit on the other hand has a bunch of anonymous users whose preferences are much harder to figure out.

[lupire]

Reddit users pour their personalities and interests into their comments. They are highly targetable.

[rchaud]

Like I said, Facebook has better tools. Reddit is rock bottom when it comes to their ad product. They should have swallowed Twitter's business when their advertisers started fleeing, but they haven't.