I think it might not be quite as amazing as it seems, Trash-80. From what little I know of AppleEvents, one could cook up a parallel-processing application on System 7 using all supported interfaces. Then you'd just need a big old stack of Macs connected together with AppleTalk, and you could have at it.Having that code re-surface would be better'n having a complete SkyLab turn up, especially the source code! [] ]'>
Such a "MAC CLUSTER" in a box full of Rockets would have obvious advantages because of the speed and latency of the AppleTalk connection. But if you were doing something sufficiently compute heavy and embarrassingly parallel, even LocalTalk might be OK.
As an example, maybe a parallel implementation of a really naive prime number test? Evenly divide up the integers between 1 and SQRT(N) between all the nodes in the cluster. Each node attempts to divide N by all the integers in its allotment. Virtually zero network traffic necessary, and it'd scale almost linearly with the number of nodes in the cluster. It would also be useless except as a proof of concept.
Heck, a skilled programmer who wanted to do it could write a Photoshop plugin to use a farm of Rockets for things like gaussian blur. You'd have to send the hunks of image data back and forth across the AppleTalk, so it wouldn't be very efficient, but it'd be a really impressive hack!