I want to suggest to add one keyboard shortcut that can be customized to use one preferred sharing services.
In my case I often ‘share’ to pocket and would love to have a keyboard shortcut for it. (And others may frequently use other services)
Shouldn’t be to hard to implement
I plan on building a suite of OAuth controls for Pocket, Instapaper, and others. When I do that, I’ll also add keyboard shortcuts, since it won’t be a simple popup window like it is now.