How good of a job are they doing at advertising? Advertising is tough since it has to satisfy both the ad buyers and the users. It’s very easy to turn off one or the other side.
One thing Reddit should note is that people are there for the communities. If there was sth. identical but run by a foundation or NGO, I'd jump there and delete my reddit account once the important communities are migrated.
As a user I hate the banners. I don't see them of course, because I ad block. I would never click them.