Arduino Bootloader availability When I look at arduino and arduino-like boards featuring ATMEGA328 chip, I see that they either use a micro controller or a FTDI chip to program the ATMEGA through Arduino board pin 0 and 1.

This only works because there is a bootloader available on the chip. Is the bootloader present by default or do I need to install it.
What I mean is can I just buy 10,000 ATMEGA328 from ATMEL, put them on boards and program them through UART or do I need to first flash them with a bootloader?
The bootloader is the feature supplied with the Arduino board, but not a chip itself. If you want to clone Arduino (fully or partially), you will have to burn the bootloader yourself.