The notion that files are copied elsewhere while cut/pasted are luda-CRISS.
Seriously.
The default action when dragging a file to a different location in the the same drive is a move (which doesn't actually move any data anywhere, just remaps the path of the file, which is why moving huge chucks of data to somewhere else on the same drive are (near) instant).
Moving to a different physical drive or partition is different. It copies the file, then deletes the original it if the copy was successful. The problem here is that up to 10.5.2 (or 10.5.1, I can't remember), there was a horrible glitch that if the cable was disconnected or a network connection was cut while moving, this would trigger a "move complete" and delete the original. This is no longer an issue.
Cutting a file is not like cutting text. When you cut text, the source "disappears." Under normal clipboard situations, cutting or copying NEW text will erase the current contents from the clipboard, losing the source forever (minus an undo, if the application is still open). Mac is intuitive enough to treat different clipboard actions differently. If you "cut" a file and don't paste it anywhere, but instead cut/copy something new/unplug your computer/jump in a volcano, NOTHING HAPPENS.
This is probably intentional behavior before 10.5.2 (though I'm not sure if this was prevalent in Tiger and earlier) due to the widely known glitch of data loss. This has been fixed. Fix Cut/Paste of files. Moving files up one directory is a pain in the ass.
