OMG! QuantumG is a genius! Here is a hack (and I mean a real life hack) for disabling just this annoying message and leaving the rest of the notification system intact...
Warning: This is a pro-tip and not for the faint of heart! It requires hacking your Mac OSX system files and could result in you breaking your Mac.
Edited for clarity.
The issue with flash drives or other USB drives is this; whenever you write data to a drive... ANY drive on your system, the data is first written to a buffer in memory. Later, when the computer gets around to it, it will flush the buffers to the device (hard drive, SSD, or any USB device). That may be instantaneous (at least to us mere mortals) or it may take a few seconds. The possible delay means that if you yank a USB device before the buffers have flushed you may end up with a corrupted drive, or a set of corrupted files on the drive.
If you only read from a device, then there is NO NEED to flush the write buffers before you yank to your heart's content because they are empty and don't need to be flushed to the device.
So... The annoying MAC OS X warning is most probably NOT relevant. It is only important to do so if you have recently written to the device, and haven't given it enough time to flush the buffers (a few seconds, max). It is NEVER necessary to wait for the buffers to flush if you are only reading from the USB device.
Therefore Apple NEEDS to provide a way to disable individual messages for power users. Don't treat everyone as a n00b who can't be relied on to know how their computer works.
And to those who complain that I'm wrong, and there is a way to disable the messages by disabling the ENTIRE NOTIFICATION SUBSYSTEM are just plain wrong. Disabling the entire notification subsystem isn't an acceptable solution, just as removing the battery from your cell phone is NOT an acceptable solution to receiving too many telemarketing calls. The notification subsystem is important and shouldn't be disabled just because the OP finds one of the many myriad of messages to be annoying.
This is a problem that can only be adequately solved by Apple providing a way for users to opt out of specific messages.