mannymo, you have a unique concept of "research." I don't know what they teach in schools now. My own academic training included a concept called "carefully studying the primary sources" -- which in this context would be the ODP itself. You could, for instance, download the RDF for this week, and successive RDFs for several weeks, to study not only the ODP itself but the changes over time.
Another academic approach is called "immersion experience". In this context, that might entail actually applying to edit a category that is of interest to you, actually experiencing the editors' efforts to find good information, their frustration at doorway spammers and SEO trash, their elation at finding truly authoritative content unpromoted by SEO and undiscovered by Google, the cameraderie of the community discussions, the passion that editors bring to their own interests and priorities and viewpoints -- as well as to the search for consensus, the sheer breadth and depth of firsthand knowledge that is a matter of course in the factfinding stage of discussions.
Forums are more difficult to analyze, but it's surprising how much you can learn about a regular poster (or even an individual poster, if you know their home page). I'd suggest that our archived "Submittal Status" forum would be a fascinating subject for analysis. There are thousands of discussions with webmasters, and for every one of them you can go look at the website. So you can see how the ODP responds to doorway spammers, affiliate farmers, genuine businesses guilty of ODP submittal spamming, and honest requests for information. You might even be able to get a good feel for what kind of sites tend to receive priority reviews. You could then, perhaps, build a stochastic image of the model surfer for which the ODP is built.
At that point, you would be in a position to begin to collect the information to make an INFORMED judgment as to how well that kind of surfer is served. (It would still be a lot of work to get the actual information: you'd have to make a random collection of sites that DID serve that kind of surfer, and then you could see how well the ODP (and other web sources) rated them.
And, of course, you could compare the ODP with other directories and search engines, to see how well we all filter out affiliate doorway spammers like tombobb. Or you could even get firsthand testimony from many of them -- just check out any standard SEO or webmasters' forum.
There's a lot of material for academic study. It could be fascinating.