Same as with Contact Form Block, something very simple and lightweight for the average user. The way I see it:
- Facebook, Twitter, Pinterest and LinkedIn should suffice.
- Floating Sidebar display options (left or right, show on mobile, etc.)
- Inline Content display options (above or below the post, etc.)
- Customization of buttons (size, shape, spacing, color and hover color)
- Display Settings (on pages, posts)