In the past, Mac OS X Finder already had a bug which caused deletion of files when trying to move them over the network onto a network share. The bug later got fixed by Apple with one of the system updates. Now, it seems to be back - or at least a similar bug.
Yesterday evening I wanted to move two files (luckily just weblinks) onto one of my AFP shares in the home network. After the operation, one of both files had disappeared.
I tried to reproduce this error - and it worked. I was able to reproduce it on other Macs with Snow Leopard (even with different types of network shares, ranging from AFP to SMB). Oddly, it yet just happened when I tried to move weblink-files (.webloc). The affected files must have been deleted by the OS, as I was unable to find and recover them - neither via Spotlight nor the shell.
It's open to dispute whether it is generally advisable to move files between network shares. Nevertheless should such an error in the OS, more precisely the Finder, never happen without any apparent reason.
I've recorded a screen-movie which shows a file disappearing when being moved.
I have now been able to reproduce this fault with rtf-files and text-clippings. It seems as if the file permissions play a role. The rtf-files disappeared for the first time after I set their permissions via shell to 755 (chmod 755 "my.rtf").