If I do not gracefully shut down my PC running on Linux, there is a risk that the PC may not boot up properly next time. Fortunately, for PC, it is easy to shut down gracefully. Unfortunately, for Galileo running on SDCard, it is hard to shut down gracefully. It is not easy to gain access to a Linux terminal to send a shutdown command. Most likely, the user will just remove the power. Is there a risk that SDcard Linux filesystem will be corrupted if Galileo board is not shut down gracefully?
I guess it is possible for some files to corrupt if the board is shut down while writing on them, but I haven’t seen that happening. What I suggest you is to back up the important data of the SD image and if something happens to that image you can always use a fresh new install in the SD upload the backed up files.