I suppose its irrelevant these days; I could just wire up my own new Denshi blocks with ease, and it'd be a good reason to polish up my Japanese .. there is a thriving Denshi culture, but it seems to have withdrawn into Japan.
For some reason Denshi blocks never caught on out in the West; but I think - as we see with this new-school effort - there are still tinkerers out there who yearn for such modularity. In the case of Denshi in the 70's, I think it was more that kids just lost the blocks too easily. Magnets help, I guess!
EDIT: Exploring the subject a little more, I realize that in fact Denshi blocks are thriving in Japan .. in fact look at this great picture:
http://otonanokagaku.net/feature/vol27/0ku8jv00000006xr-img/...
I now have a reason for a 3d printer. :) (Another one, anyway)
[1]http://threestepsoverjapan.blogspot.com/2011/12/gakken-kit-3...