Their filesystem integration would have been just as seamless without the badging. I admit the badging is a useful feature, and certainly made Dropbox better but by no means is it core to the product.
You're talking past each other — other, more fundamental features used to require hacking OS X.
See for instance https://news.ycombinator.com/item?id=12467149. IIRC ArsTechnica wrote at some point that monkey-patching Mac OS/Mac OS X was standard on the platform.
