A good idea, but sometimes you want to access information when there is either poor or even no connectivity. Having the device sync with your own server is the way to go, but there needs to be a mechanism to erase the device quickly, and then restore later. I suppose that opens up the possibility that a comprehensive wipe could take too long (e.g. that the the people forcing you to open your device to them could somehow stop the wipe before it completes). Additionally, with devices carrying tens (if not hundreds) of GBs of storage, an over-the-air restore could be extremely painful. Maybe a multi-stage restore mechanism, where a smaller set of key data can be restored quickly (contacts, calendars, notes) while larger data (photos/videos, music, games, files, applications) can be either trickled in or held off until the device is connected to higher speed/lower cost network.
I've also been thinking it would be good to build a virtual RAID out of cloud services. Say you have three services -- configure them such that exposure to any single service doesn't expose your data ... you need to have at least two of three services to re-assemble your data. So even if someone confiscates your server, you don't lose data and they don't gain access to the data - I'd still encrypt the "chunks" or "slices", but this would add redundancy and reliability