I don't know to be entirely honest, I just noticed that indieKarma was run by a company called PixelPass and thought I'd look into what other products/services they ran, but didn't look into it too much. The idea of cutting off content from readers wouldn't be my kind of thing either.

From the looks of this page it adds an obscuring strip to the middle of your blog, which would probably annoy me more than a pop-up. Maybe its modifiable, but I'd imagine that with my knowledge for your un-willingness to put ads on preshrunk that it wouldn't be suited to you.

Ahh well, the search continues for the perfect revenue service.