I'm not sure I understand. I can drag a file from my file manager onto my Photoshop icon, and it will open the file in Photoshop. I have a stack of program icons on the right edge of my left-hand monitor for just that purpose. I think that's the opposite direction from what you're asking (drag the file onto the program, instead of drag the program onto the file) but is that significant?
there are two cases where dragging a node make sense.
hence you have a dock with bookmarks only and you have multiple accounts on the interweb. then it would come in quite handy to simply drag a bookmark node on the related browser window. while developing i very often have to check the same link in different browsers.
so instead of maintaining the same bookmarks in all browsers i would simply drag the bookmark from my central bookmark dock.
second case: working with lots of graphics or other often used documents.
some screenshot programs and programming tools have the functionality for dragging a finder on a target for further processing.