Moving our usage totally to the cloud is not a great idea, it seems. Yes, we get convenience, but at the same time lose autonomy, control, and freedom over our computing.
RMS has a good (albeit slightly extreme) view on this: https://www.gnu.org/philosophy/who-does-that-server-really-s...
This view has people discussing the issues e.g. http://arstechnica.com/information-technology/2008/09/why-st...
All in all, if we as users demand web apps that respect our freedom, and employ non-proprietary file formats, then this would be a non-issue. There are a number of ways this could be implemented... one would be to provide a software package (with source code), available to be downloaded and run locally on one's machine, if the product changes or gets trashed. Of course, complete access to your online data is necessary (i.e. ability to download your data as when you please).