This has been a fascinating discussion; coming at a very appropriate time for me. I'm in the middle of teaching my first class on ID, to a group of teachers and media specialists who think the process is pretty useless.
Rob identified several reasons why TBT has not been more enthusiastically received in commercial markets. I would like to suggest another possibility why schools aren't more embracing: It doesn't fit into the current educational culture. In my experience, most educational software is implemented in the classrooms by sticking students at a computer and expecting them to work through a certain number of modules. The concepts in the software might be perfectly sound but for students to make the links between the concepts and previous experience requires interaction with teachers and other students, i.e., sensemaking requires social support.
Of course I know that there is good software out there and that it can be implemented more successfully, but many teachers (1) don't know how to select good software, (2) are leery of experimenting with integrating technology into their practice, or (3) are in need of a way to manage large class sizes with diverse student populations and therefor use the software as baby-sitter.
As an example of poor integration: I spent time a few years ago reviewing the Sim____ software. There are some very powerful concepts built into these packages, but the students I observed using them were simply playing games--not trying to understand what was happening on the screen and how those actions represented a model of what happens in real systems. But what if an instructor were to integrate computer modeling into a science curriculum, and used SimEarth to help students visualize the impact of interactions between temperature, plant growth, human reproduction, migration patterns, etc.? The tool is cheap, it is compelling, and from my incomplete knowledge of science and systems, it is relatively accurate. The integration plan, though, requires teachers to change their way of thinking, it requires computers in the classroom not in a lab, and it requires students to take more responsibility for their own learning. In practice, that is a big cultural change even though the research has been talking about it for years.
I guess I'm suggesting that marketing needs to occur at the pre-service level so that teachers are trained from their earliest experience (educating potential clients???) to think of technology as tools (means not ends) for improving student learning. It means that teachers have to have deeper understanding of their content areas so that they can be more flexible in how they design learning opportunities. And for designers, it seems that we need to be more clear on how our decisions are made. Back to the Sim example, the formulas and calculations upon which decisions are made within the simulation should be made explicit so that teachers can incorporate that information into their own lesson designs.
Many large and small corporations have created their own markets very successfully. Maybe it's time for the very diverse population of IDers to organize into a professional organization that could take the lead (like the AMA perhaps--yikes, what a scary thought!).