I must disagree. Did you collapse the target folder or scroll the places list so the target was not visible? It is rather tough to call it user error. I have specialized in UI design and development for 10 years. GE's behaviour is dramatically different from that of Windows Explorer.

If you look at the image below, Target folder one is off-screen. I can not drag items there in GE. Target folder two is on-screen, but collapsed. Again, GE will not let you drag items there. Target folder three is on-screen and expanded. Finally, GE will let you drop items onto the folder.