IMO, the two biggest problems with the research on online learning are a near total lack of theory guiding the research and deeply flawed methodology - a toxic brew of scholarly ineptitude.
The study of the modality is young, and definitely not mature. There are few legitimate theories. This makes the research naturally flawed, especially when compared to the more mature fields of inquiry. But this in and of itself does not mean that the
study of online learning is a waste of time, as some of the more cantankerous elder states-persons of education seem to say.
It is so bad that a competent scholar could argue that the entire field is based on nothing more than publication bias favoring the studies where random chance produced either positive or "no significant difference" results. But then again, learning outcomes really aren't the reason everyone's interested in online learning, are they?
we rarely hear about the small advances, only the huge flops and incredible successes. The anecdotal evidence is of course not suitable as a jump-off point, since it hasn't been published in some internationally-recognized publication, double-blind-peer-reviewed of course. This is probably due to the comments I noted above.
A vicious circle to say the least.
But then again, learning outcomes really aren't the reason everyone's interested in online learning, are they?
Quite right. I suspect that most institutions go towards online as a way to 'cut costs', or worse yet, 'to keep up with the Joneses': Fear of losing out on a potential opportunity is a powerful driver. When online learning is driven and designed by the instructors, the outcomes are more likely to be valid because the instructor has a much higher stake in the outcome, and will be more likely to make adjustments quickly when something is not working. When an institution shovels it through the academic alimentary canal, it will likely be digested as is, then when it produces something undesirable, the persons involved will say "See, I told you so!". Vicious circle yet again.