Since some recent KDE upgrades (last 3-4 weeks maybe?) in fedora, I've been encountering a strange problem. KDE seems to be "pretending" to copy small files to ANY USB device (including NTFS and FAT32 formatted devices). It appears to copy, and I can open the file once it's done on the device. However if I remove the device and plug it back in, the file is gone. Has anyone else experienced this problem?

Did you safely remove the device prior to removing it from the computer? If not, this is a feature of the underlying system, namely the Linux Kernel, which is storing the files in memory prior to writing them to disk to improve performance. When you safely remove it, the system writes all pending changes to the device immediately.

The reason for this change in behaviour is likely because either UDisks or HAL ceased setting a mount option which forces the files to be immediately written to the storage device.

No i was not safely removing, but for 2-3 3 meg files i wouldn't expect any caching to happen unless the system is really busy doing something else or another huge bulk of files are being copied. It seems a bit silly for the kernel to do this when the system is essentially idle and only a few small files are being copied. I'd also expect it's not caching the files for upwards of 30-60 seconds, which is how long i waited before removing the USB drive.

KDE cannot control the kernel in this case. Safely removing the media is the best way to ensure that all data is safely written out successfully.