Track JetPack Shares in Google Analytics

tracking.js

/**
 * Javacript for loading custom Google Analytics events
 *
 * @since 1.0.0
 */
(function($) {

	// GA Docs for Social Interactions:
	// https://developers.google.com/analytics/devguides/collection/analyticsjs/social-interactions

	if ( typeof(ga) == "function" ) {
		// Twitter
		$('a.share-twitter').on( 'click', function() {
			ga( 'send', {
				hitType: 'social',
				socialNetwork: 'Twitter',
				socialAction: 'share',
				socialTarget: $(this).attr('href').substr( 0, $(this).attr('href').indexOf('?') )
			});
		});

		// Facebook
		$('a.share-facebook').on( 'click', function() {
			ga( 'send', {
				hitType: 'social',
				socialNetwork: 'Facebook',
				socialAction: 'share',
				socialTarget: $(this).attr('href').substr( 0, $(this).attr('href').indexOf('?') )
			});
		});

	}

 })(jQuery);

Nice gist! I've adapted it into a basic WordPress plugin here crediting your work in the README and code.