I don't understand how "You have to remember to put all your files in a special folder" (Dropbox) is much different than "You have to remember to put all your files on a special drive".
He was most likely referring to the ZumoDrive "folder linking" feature, where you can link an existing folder on your system with ZumoDrive, instead of moving it.
Ok, that makes sense. It was just the way he wrote it looked like he was comparing having a special drive letter with having a special folder which didn't make any sense.
Being able to use arbitrary folders is indeed a very useful feature. I'm on Linux so I've just been using symlinks but on Windows I can see it's pretty vital to have it built into the software.
I use NTFSLink (http://sourceforge.net/projects/ntfslinkext/) which makes it very easy. Right-click in a folder and select New... and then you can choose NTFS Hardlink or NTFS Junction point.
Great app and combined with DropBox, I can sync data folders without having to move them.
With the new version of Zumodrive you can simply link any folder to Zumodrive.
I link my desktop to Zumodrive. So any time I create a new folder or add a file to my desktop, it is available to me on all my computers. Same with my iTunes music. I dont have to move anything any more.
Before the folder linking you had to move or copy studd into a special drive.