Dropbox Folder in MBA without installing Dropbox...

that folder has nothing to do with the company Dropbox and is on every install of OS X as standard for sharing documents through a network connection.

 

Yes, that folder is called a "Drop Box" (note the difference in spelling between that and the company name "Dropbox"). Dropbox (the company) named itself after the more generic term "drop box" which is essentially like an open mailbox where, if you allow file sharing, other people can write files to your home directory without actually having to give them read or write permissions to any of your other files.

Be careful about file sharing when you're on public networks like hotels or even libraries, schools, etc. Your Mac will announce to the entire network that it has folders available for sharing, and people could write all kinds of clutter to that folder, even just as a prank. Don't ask me how I know this.

 

Here's a few links for reference:

OS X Lion: Share files with others who use your computer
OS X Lion: Share files with others on your network
OS X Lion: Share files with others using a drop box
OS X Lion: What are the Shared and Public folders?
OS X Lion: Control access to your Public folder

 

Actually I has Air Drop folder by default, not Dropbox. The last one appeared after installing this favorite app from the net and which I use every day. The icon is also from dropbox app. Our colleague must check this situation.