I'm on Warren's side
pic of a newer Vitamix drive socket:
drivesocket.jpg
Notice the metal parts are encased within molded plastic or hard rubber. My guess is the casing acts as the same way as a woodruff key, shear pin or the rubber hub inside boat props, to absorb the shock of a sudden stop. His original looks to be made the same way, but a much older design obviously, with less plastic used. The 'blob' is simply part of what's left of the original plastic casing, and if it WAS intended to absorb a sudden shock, it looks like it did it's job. I'm assuming what looks to be rust IS rust on the parts, so if not caused by a sudden shock, corrosion could have compromised the bond between the plastic and metal...
Warren- just drill into the 'blob', it's not like you're going to hurt it any more.. my money's on you finding it's plastic or hard rubber...