The reason that enterprises have IT departments is so that they can control everything in house. The saas model (dropbox and similar remotely hosted services) doesn't really fit here because it separates IT from the services that it is supposed to manage (think of the legal and security mess of spreading your company's data to a bunch of 3rd party services).
Your best bet is to find some white-label/internal solution similar to dropbox and get your IT guys to install it... but it'll be tough to convince them that the benefits outweigh the costs (everything IT does costs 10x more than you think it should).
Really, your best bet is to route around them. I may be a techie but I have little respect for corporate IT, sorry. Instead of focusing on increasing productivity, they always seem to focus on increasing their control (in order to not loose their jobs), and to increase "security". They don't remind me of hackers, they remind me of airport scanners and laywers.
I hear the control part but what control is there really... Don't you think the physical files on the laptop of the average corporate worker are more likely to be compromised than dropbox itself?
Not sure companies will survive and be competent if it all goes this way...
Do we need FDIC (from the banking world) for data?
Your best bet is to find some white-label/internal solution similar to dropbox and get your IT guys to install it... but it'll be tough to convince them that the benefits outweigh the costs (everything IT does costs 10x more than you think it should).