What might go wrong? (This is a test of imagination, not confidence.) Google might finally unleash GDrive and steal a lot of Dropbox's thunder (especially if this takes place before launch.)... From Dropbox's 2007 YC Application, http://dl.dropbox.com/u/27532820/app.html I love reading old YC applications. I wonder if someday, they'll become the 21st century version of Harvard Business Review case studies.
I think an accelerator application or business plan would be better than a case study simply because case studies are often written with hindsight. The HBR makes it difficult to honestly assess what real-life people thought before making a particular decision.