With companies like similarweb [1], collecting click stream from millions of (unaware) users via various browser extensions, you can pretty much forget about the "private link" concept.
I thought we learned this week that "private links" for sharing documents are horribly insecure. I'm pretty sure they want it to still be password protected, which ShareFile is.
BTW, Google Apps has a feature where you can share to "people within my domain who have the link", which is a very nice middle ground between "everyone on the Internet with the link" and "I need to explicitly choose who to share this with.
[1] http://similarweb.com