I think one of the barriers to "monetization" is that the user base finds the concept offensive.
A community does not need to be making its creators money hand over fist, or indeed making money at all to be successful in terms of what the users expect/want from it.
You've touched upon a very important point. There is huge antipathy on the part of /b/tards towards sites like icanhascheezburger, knowyourmeme, and others that profit off of content created on 4chan and shared for free with its users. /b/ is mostly shit, but there are nuggets of gold there and most /b/tards browse in order to witness their creation. /b/tards generally lament memes that go mainstream. Rickrolling became incredibly painful once the old media picked up on it (long before, really, but the cat was out of the bag), as did chocolate rain. Sites that capitalize on the content created by /b/tards for other /b/tards draw a lot of ire, and are frequently the targets of attacks.
In the same way, most /b/tards would leave if 4chan became anything resembling a legitimate business. There are far too many alternatives out there, and while moot is generally well-liked, not too many people feel a great sense of loyalty towards him. /b/tards have left in droves over far milder insults than trying to make money off them.
The other problem is the content on /b/. It's nearly impossible for moot to find advertising partners, given that gore, beastiality, and child porn are posted fairly regularly. Not many legitimate companies are will to risk being associated with that, so /b/ has had the same banner ads for months on end. I can't imagine they pay much.
Minor correction, there is very little cp posted on /b/ anymore. You'll find that stuff more freely on other spinoff chans, but rarely on /b/ specifically anymore. It's a lot more tame tbh.
The thing is, cp includes self shots of people under 18. There is TONS of that on /b/, of both genders. It's awfully hard to tell 19 from 17 when you're taking a topless picture of yourself in the mirror.
Nobody, mods included, cares about the borderline cases where the subject may or may not be 18. They care about the pictures of intercourse with 9 year olds.
Meh, I don't really consider all the camwhores on /b/ and the new /soc/ to be cp really. It's when they start to have really small or no tits and larger head to body ratio sizes - 12ish and under - that you're in cp territory. This is true cp, and what the real btards on places like 7chan indulge in. The current race on /b/ is full of the last waves of summerfag and other general newfag cancer. There was a time a lot of actual cp was posted on /b/, but that times' long gone.
Unfortunately, this isn't just a question of interpretation. Legally, there's no differentiation between those two categories. One is more ethically problematic than the other for sure, but you're just as screwed having either on your computer. You can see this most clearly in sexting cases against high school students. You can still get on the sex offender registry for sending a picture of yourself to your boyfriend or girlfriend and there's tons of stuff like that on /b/.
A community does not need to be making its creators money hand over fist, or indeed making money at all to be successful in terms of what the users expect/want from it.