So what happened?
Muddled by metaphor
First, it got muddled by metaphor. Blended learning failed when it got bogged down by banal metaphors. I've heard them all - blended cocktails, meals, even alloys. Within the ‘food metaphor’ mob we got courses, recipes, buffet learning, tapas learning, fast food versus gourmet. My own favourite is ‘kebab learning’ - a series of small bites, repeated in a spaced practice pattern for reinforcement into long-term learning memory, held together with a solid spine of consistent learning content and objectives. Only kidding of course, but that's the problem with metaphoric blended learning. Who's to say that your metaphor is any better than mine? I even had some fool at the Learning Technologies exhibition come up to me with a 'fruit blender' trying to explain the concept in terms of a fruit smoothie!
What happened to analysis?
Blended learning needs careful thought and analysis, the consideration of the very many methods of learning delivery, sensitivity to context and culture and a matching to resources and budget. It also needs to include scalability, updatability and several other variables. All this talk of meals and metaphors has been going on for several years. What it led were primitive, indigestible (sic) 'classroom and e-learning' mixes. It never got beyond vague 'velcro' models, where bits and bobs were stuck together (now that's a metaphor).
Blended learning became blended TEACHING
Second, blended learning books turned out the very opposite of Blended Learning theory, namely Blended TEACHING. Attempts at defining, describing and prescribing blended learning were crude, involving the usual suspects (classroom plus e-learning). It merely regurgitated existing 'teaching' methods, usually around some even vaguer concep like 'learning styles'. Note how vagaue concepts reinforce each other in training. When it did get theoretical it went wildly overboard, with the ridiculous ramblings of the Lego Brick brigade (Hodgins, Masie etc), espousing the virtues of reusable learning objects.
Let me put forward my own food metaphor – blended baloney. What do you get when you blend things in a mixer without due care and attention to needs, taste and palette? What we got was baloney (dull, tasteless sausage meat).