I just got my Galaxy from eBay. The auction said it's 16GB, but I am afraid I was a fraud victim; I'm checking at Settings->SD card and device storage->USB storage, and Total memory says 5.01GB.
Am I missing something?
My Galaxy S Vibrant has 16 GB internal SD storage, and
Settings -> SD card and phone storage reports 12.78 GB. I would assume the ~3 GB difference is due to the reported size being actually in GiB, not GB, and partitioning (the internal data partition is 1.84 GiB as reported by Titanium Backup) and formatting. The numbers work out, anyways.
Given that 8 - 5.01 is also ~3, I would say that you have an 8 GB model on your hands. Checking with Titanium (requires root) or something else might be a good idea.