One would think so, but there are mitigating factors:
1) The topic matter is "whatever it is people read and talk about on the internet." That's a pretty broad based topic.
2) Most people who get into that sort of thing, to judge by the fora and lists I read, tend to focus on selling ebooks and crap that teach people how to make money selling ebooks and crap.
2)a) Most people who build AS-driven sites tend to build utter garbage that is basically some copied or otherwise filler content drowning in ads. No one is going to stay at a site like that, let alone get interested in sidebar content that might make the owner some money. This kind of crap site is in superabundance at the marketplaces I mentioned above, but what I'm talking about buying are actual quality sites with a decent layout, original content etc.
3) And to reiterate an earlier point, it's not neccessarily something from which one can retire wealthy in a few years, but a steady and sensible acquisition and reinvestment strategy can be very profitable, way above traditional stock returns as a %
Phaedrus