I accidentally deleted a bunch of really important files while the phone was on (using Cyberduck) by not noticing that besides the file I selected being highlighted, two other large and important files were also highlighted. By the time I realized what was happening, it was a major ooops moment. I went to restore it and it wouldn't come out of bootlogo. However, after about half an hour of messing with it, I got it to restore. I think, unless you crush it or drop it on something hard enough to break connections, or submerge it, the phone will always be restorable. That is, unless you break a port somehow and can't connect it to your computer.