what you were probably reading about is how kingston is using cheap memory modules for its flash drives and they are having a high failure rate.
m0n0 is a lot smaller footprint (10-20MB), it does not take up the same amount of space as pfSense does and as a result wont hit 2020163584 bytes. pfSense requires 128MB minimum. and the current smallest image (for 1.2.3R) is 512MB, which is about 500MB more than m0n0.
from the total bytes you are writing the 1GB image to the card, m0n0 is only writing .02 GB at the most, the card is probably bad.