I have read on the official Raspberry Pi website that it is possible, by adding a line,
program_usb_boot_mode=1, to the
/boot/config.txt file, to flash a Pi3 with the instruction to boot from USB instead of SD Card and - after it's done - a change to the One Time Programmable bit would cause the Pi not to require an SD Card at all anymore, being it able to boot directly off of a USB drive.
I'm interested in doing this though I wonder: since everyone on the Internet (Foundation included) says it's a permanent change that cannot be undone, if I may ever wish to revert this change on my Pi so I can boot from SD, would I be able to do it or would I have to purchase a new Raspberry Pi? And if it is possible what would I have to do? Would booting from a Mass Storage Device containing a config file with the same line except zero value suffice?