Raspberry Pi interview: Eben Upton reveals all (Linux User)

There are a lot of add-on parts (vga, serial, wireless) that people would like to see added to the raspberry pi but in order to maintain their inexpensive price they chose to put the bare minimum peripherals needed to make a functioning computer. I think they made the right choice. Not everyone is going to need a serial port so why make everyone pay the extra cost for the part and pick/put robot placement on the board plus the increased board size that it would require? Since the GPIO lines you have access to on the rapsberry pi have a 3v TX and RX pin attached to a UART I think all you need is a $5 part from Amazon to add serial over USB if that is what you want.

http://elinux.org/Rpi_Low-level_peripherals
http://www.amazon.com/UART-Module-Serial-Converter-CP2102...