Because your competitors won't -- that's exactly the reason not to spend a major chunk of your time in a porting effort. Some history springs to mind involving IBM, Lotus and, indeed, Microsoft.
Unless IE-Firefox seamlessness is the original point of your extension, this compatibility is almost certainly not a hair-on-fire concern for your users. Foxmarks shows a reasonable workaround: provide a website where you can reach all your data in a pinch, and focus on usability and extended functionality for the browser add-on.
Unless IE-Firefox seamlessness is the original point of your extension, this compatibility is almost certainly not a hair-on-fire concern for your users. Foxmarks shows a reasonable workaround: provide a website where you can reach all your data in a pinch, and focus on usability and extended functionality for the browser add-on.