I recently had an issue with some uCs that just wouldn't respond to the bootloader. I suspected they were fake, but I got them from digikey. I asked digikey if they could confirm origin, but they ignored me :(

They responded to JTAG correctly, but none of the other documented bootloader modes, which was a dealbreaker. I don't think they were actually fake, but certainly defective or at least incorrectly documented.

Every single time I've tried to use an ST device I get bit. I'm sure it's just me being unlucky, but I avoid their parts now when I can.