I have created filesystem on USB harddrive some time ago and yesterday my collegue tried to mount it.As per my documentation all he had to do was to run 'mount -t ext3 /dev/sdX /mnt/usb' This does work however he is adamant that this is wrong and should not work as I should only be able to mount /dev/sdXn where n is the partition number.His argument that you cannot mount whole device. I belive answer may be very simple ?
Basically you created a filesystem directly on the device and did not create a partition table. You wouldn't be able to boot to this. I am sure there are other limitations as well.
What you have described will work in that you can mount the filesystem under Linux and store things there. It not a standard thing to do for hard drives. By setting up your system that way you may confuse someone else using your drive. In extreme cases that person might try and open the drive with a partition editor (fdisk/parted) and actually destroy your filesystem because they didn't know you did something non-standard.
Keep in mind that your floppy disks, cdrom don't usually have a partition tables either. So what you have done is not completely out of the ordinary.