Blinksale does ads in their interface
It’s not the first web app to place ads inline. One that springs to mind is the old intranets.com (are they still around?) which seemed to be all about selling you stuff. But for a modern-day web you-know-the-number type web application? And on the inwards-facing side of things? I’m more accustomed to someone like Flickr putting ads against my photos, but not against the screen I use to upload my photos. Maybe it’s because I’m on the free plan, and they go away if I pay? Interesting.