I have been unable to find any info on the Internet and my Raspberry Pi is coming in the mail soon. So, I cannot answer this question myself. Will the Raspberry Pi boot Raspbian off of a Ext4 formatted SD-card?
There is no point in you formatting the card. The raspbian image contains 2 partitions, one small vfat and one larger ext4. You just follow the instructions and write that image directly onto the card.
To reiterate: DO NOT format the card and then copy the image in as a regular file or something. That is not how it works. The image contains two filesystems, and when you write that to the card, the card will then be formatted with the two partitions. Just follow the instructions to the letter.
Also DO NOT format the card and then copy the contents of the image onto it. The first partition, as Lawrence says, must be vfat (because of the minimal firmware bootloader used by the pi). This is a "boot partition" and it contains the linux kernel. The kernel then mounts the second ext4 partition as the root filesystem, and that contains raspbian.
I.e., this is NOT the way you would normally boot a PC with linux (whether it's on an SD card or a USB key or a DVD or whatever), so don't approach it that way. There's no grub, etc.
If you want to change the size of the second partition, install the image to the card, then put it in a PC and use
If you mean have the whole card formatted as ext4, then no.
The boot partition must be vfat
However the rest of the partitions can be ext4
default raspbian image does exactly this:
$ mount /dev/root on / type ext4 (rw,noatime,data=ordered) [...skipped...]