I was missing the icons, too.
Sahre and Follow Version 1.21.6
Theme: The PaperCore by Pexeto
I had installed the plugin using the Add Plugins auto installation and then had upgraded from WP 3.0 to 3.0.1 some time after that.
I deleted the Plugin from within WordPress. Then instead of using the auto-install, I downloaded Share and Follow, unzipped it, and uploaded the share-and-follow folder to wp-content/plugins using an FTP program. The icons appeared after that. And all of my Share and Follow settings were intact, too.
Wat was truly odd before I tried the fix described above was that when I copied the URL to any of the icons and pasted that into a browser I got a File Not Found error even though my FTP program and server Control Panel's File Manager indicated that the icon files were indeed there.
Anyway, given my configuration as listed above, deleting the plugin from within WordPress and then uploading it via FTP solved the missing icons problem.