Max storage is WAAAY more than 4GB
This describes how to add a multiplexed external SATA enclosure, to give 4 more SATA drives, using the built in eSATA connector, and also two further enclusures, for a total of 16 drives, each 2TB or more, for a total of 32TB+ of storage.
My suspicion is that Acer quoted the 4TB 'limit' way back when 1TB were the top end drive. As someone else has said, these machines have been available elsewhere for at least a year.
The one limit that is there, though, is the 2GB RAM limit - this is as much as the Atom CPU installed can address, and the CPU is soldered to the board.
There are also ways to add PS/2 keyboard, mouse, VGA and a true serial port, for those moaning that it is a headless unit. See this link:-