I think we would soon have sharing in-built within the OS. Mountain Lion already has it while it would not take much time for Windows 8 to implement this into their OS as well (if they already do not). The lines between a tablet/phone OS and a desktop/laptop OS are blurring and we can very well see that with Mountain Lion and Windows 8. Therefore, not just the browsers but every bit of functionality in the OS which needs a "Share" will have it by default.