What future for cloud storage providers?

I’ve been happily using SugarSync for a couple of years now to sync files between my work and home PCs.  It runs quietly in the background and has seldom caused me any problems.  I know that Box and Dropbox offer similar solutions and also have good reputations.  However, a few announcements over the last months have made me wonder how these services will evolve as they try to move from a largely tech-savvy customer based to more mainstream users as well as being taken up by mainstream businesses.  One of the ways they are making this transition is by integrating their offerings into other services such as SharePoint and embedding them into the operating systems of mobile phones and televisions.  Opening up their APIs to allow this integration is a direction of travel for many such companies and makes much sense.  Users expect applications to talk to each other and while there are a number of disparate companies offering specialised services such as storage, synchronisation, CRM and task management there is a logic to it.  However, what happens as these services mature and the big players such as Microsoft, Google and Apple expand their own similar offerings?  There is a danger that companies such as Box, Dropbox and SugarSync will move further away from the end user as they become integrated into workflow applications like Outlook and Sharepoint or are hidden in the background of television and mobile phone systems.  The more invisible they become the harder it will be for them to develop customer loyalty and the easier it will be for the customer-facing applications to own the relationship.