The editable images feature recently released (see link below) brings up a big idea. It would be a small variation of this, but potentially a very powerful tool based on feedback and requests from teachers and students.
There are many PDF assignments in curriculum providers using buzz. Can Buzz add the option for students to draw on and add text to a copy of the PDFs directly in Buzz? Then submit the completed modified version directly in Buzz dropbox, without leaving Buzz? The big difference here I guess is that these are PDF's and the new feature is for images. Perhaps Buzz converts the PDFs to an image for the student, and facilitates the editing and submission of the activity? This would be huge... Perhaps Buzz is already looking into this?
As it is, students need to download the PDF, open with PDF editor, save, then upload into dropbox. And this process seems different on different computers, complicating the whole thing. If Buzz found a way students can edit the assignment right there in buzz and submit them, it would be huge.