With my OG Droid, I had an interesting experience in the subway once, where I was having issues accessing my MP3's from the storage card, so I dismounted it. When I went to re-mount, it appeared that the phone for some reason needed to contact Verizon and/or Google, so with no signal underground I was unable to use any of the apps that I had on the card (their icons had all gone to the default android picture, and none of them would launch), and I couldn't access any of my media files. As soon as I left the train station and was outside with a renewed signal, I dismounted and remounted again and everything was back to normal.
I don't know if this is expected behavior or not, but it was/is reason for me not to want to put any apps on the card any longer, if I can avoid it. Oh, and I haven't tested this with the Rezound, based on how frustrating it was (not to mention the fair amount of panic I went through).
*shrugs*