It is quite difficult, as well as painstaking. I can't find the article where Drew Houston was mentioning this, but because the API method wasn't available, the

It is quite difficult, as well as painstaking. I can't find the article where Drew Houston was mentioning this, but because the API method wasn't available, they had to use a hex editor and alter the memory location to get the functionality to appear in the finder. And they needed to do this for every version of OS X as the Finder memory address to inject the assembler/C code would be in different locations depending on the version. The process would be similar to writing a crack for software to find the algorithm for the serial key check. Besides Dropbox being a great service, what got Steve Job's attention was the fact that the internal cloud team was impressed on how Dropbox managed to do this, since they themselves couldn't get the OS X team's cooperation for a similar feature. Edit: found the article - http://www.wired.com/epicenter/2011/12/backdrop-dropbox/all/1 http://www.wired.com/epicenter/2011/12/backdrop-dropbox/all/...