Using toolbar to add drag and drop functionality ?

There is a huge market for storing/backing up your files online. People buy .mac specifically for this (and other things too..). But lets say Yahoo! (or for that matter Google too) were to decide that they were going to use their respective browser toolbars to enable users to drag and drop files onto their respective online storage space ?

Yahoo already has the briefcase (which i dont think many people use….plus its only 20mb). Google is well placed to let users use a portion (if not the entire) storage space of gmail for this purpose.

Anyone know of such a thing existing out there ?