My own opinion is that it is the change in emphasis from YECism to IDism that has caused the decline in participation by Creationists. With YECism there were literally dozens of topics to debate, such as the shrinking sun, the declining magnetic field, the variation in
12C concentrations, the unreliability of radioactive dating, the depth of moon dust, the lack of transitionals, white holes, hydrologic sorting, runaway subduction, accelerated evolution within kinds, and so forth. Creationists could visit any number of Creationist websites and get all charged up on any and all of these subjects so that they could then traipse into discussion boards like this one and display their ignorance.
ID takes away all this easily comprehended ammunition. Any Creationist who decides that ID, while not ideal from a YEC perspective, is the best bet against evolution has to give up all those arguments. Those Creationists who expend the effort to familiarize themselves with the details of ID understand that they have to give up a young earth and concede that most of evolution occurred naturally. I think many do so very reluctantly, and so they cannot muster sufficient enthusiasm for it to participate in discussions about it at online discussion boards.
I expect there will at some point be a backlash by traditional Creationists against ID, especially as they realize that ID has no better chance of overturning evolution than YECism.
Those Creationists who are enthusiastic about ID, like Randman and Buzsaw, don't understand it. Mostly such people are YEC's who somehow don't perceive the contradictions between YECism and IDism.
--Percy