There are plenty of bookmarking/sharing/readlater services around and I hardly see how you could provide most of them with a checkbox list in Preferences window like now.
How about a flexible system where you provide the service’s API link, name and icon ? Like :
Icon URL: https://kippt.com/static/img/favicon.png
So everyone can add his beloved sharing system to his Newsblur account.
Wonderful idea, and I would have loved to have built it, I just haven’t had time. It’ll happen soon enough.