What about concurrent threads?
In this shared bookmark example what happens when I open Chrome and FireFox at the same time and they both use the same settings file? When I bookmark a new page in FireFox what happens to Chrome? You can't actually have the same file open twice. Does it make copies like MS Office? Then how do you manage syncronizing? Do you develop this new settings manager as a background process in the OS? I see this causing more problems than it solves.
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