You do not need /boot; if you don't specify a /boot partition, there'll be a /boot directory within your /root partition (and thus, most people go with a simple /root, /home, and /swap partition setup). You may ask, what's the point of having a /boot partition then?
1) It makes booting multiple Linux distros somewhat easier to manage.
2) If you want to encrypt your Linux partitions, you must have a separate /boot. Why? Grub can't read encrypted partitions; you can thus encrypt /, /home, even /swap (an encrypted /swap means no hibernation, unfortunately), but you must not encrypt the files that Grub reads on bootup, i.e. the stuff inside /boot, otherwise you won't be able to boot. So /boot has to be a separate partition and be unencrypted.
3) If you choose a filesystem that Grub can't read from, for your /root partition, you will need a separate /boot. Example: brtfs, the next generation Linux filesystem and ext4's successor, is now relatively stable and can be used, however Grub cannot boot from a partition formatted in brtfs. Thus, your /root partition can be in brtfs, but /boot will have to be in a separate partition and be formatted preferably with a filesystem from the ext family (a common pick for /boot is ext2).
Debian Testing x64/LM9 Main x64/Windows 7 x64 - LG R580 laptop w/ Intel Core 2 Duo T6500 2.1 GHz, 4 GB DDR2 RAM, Nvidia Geforce G 105M, Ralink rt2860 802.11n, 300 GB WD HD 5400 rpm