And anyone who has read more than an introduction to mongo knows that you SHOULD use getLastError to be safe. If you do that, no data will be dropped.
[root@li321-238 tmp]# dd if=/dev/zero of=./filesystem bs=1M count=128
[root@li321-238 tmp]# mkfs.ext2 filesystem
[root@li321-238 tmp]# mount -o loop filesystem myfilesystem
[root@li321-238 tmp]# dd if=/dev/zero of=myfilesystem/im_too_large bs=1M count=129
dd: writing `myfilesystem/im_too_large': No space left on device
A program that continues along without issue, only changing its behavior in some unannounced (documented or not) way, is not "limited". It's free as a bird.