Ted Habermann, The HDF Group
I first heard of HDF during the “Data Format Wars” of the 1990’s. These “battles” centered on the selection of a format for the emerging NASA Earth Observing System archives, and there were a number of contenders. HDF won that battle in the end because of the inherent flexibility of the format and the tools for reading and writing it.
Now, twenty years later, HDF has emerged as the foundation format for an incredibly diverse and growing selection of scientific and commercial disciplines.
Is it the inherent flexibility of the format that has led to this success? Maybe, but I would pick information integration as the killer HDF feature.