If there were one IM related topic you would want to learn more about, what would it be?

Split testing

I would say traffic. If you can get traffic for free or at a very low rate then sooner or later you will probably make money, whether via Adsense or CPA or affiliate offers.

Market Research is the very first step and the foundation of your business. However doing the correct market research alone doesn't guarantee anything when speaking from a technical IM standpoint.

On a pun note, market research is a wide term which includes everything from education, coaching to taking action and each and everything in between. So yea, market research essentially covers everything within itself. So it is indeed the most important thing from a theoretical and action standpoint.
Nevertheless when asked for a specific academic standpoint (and not philosophical standpoint) you need to answer something very specific and narrow. Market research is technically just niche research and keyword research which is nothing. But what you wanted to say was more like a pun or fun fact where it is indeed true.

Coming back to the point. If you can get traffic then chances are that you are sorta guaranteed at least Adsense income.

i agree, i think you should do some market research.....

I didn't mean funny. I didn't mean fun. I meant it was more like a pun.

Like Zannix, getting case studies about traffic generation methods is something that could really help.

However, I think that case studies for each and every traffic source with the conversion rates for the capture page and one time offer could permit to compare the effectiveness of the different methods.
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video marketing in particular

What about Social marketing?

Probably SEO and using social media better. Or even just generating targeted traffic in general.

Seminar marketing and back of the room selling.

Marketing thru viral videos