Cacher is the code snippet organizer for pro developers

<!-- Jetpack is a WordPress plugin that brings a ton of features to WordPress. You turn on the features as needed. At the time of this writing, rather than include a separate CSS file for each feature as needed, they load a large concatenated stylesheet with all the CSS together. -->

<!-- I was in a position where I was using a few Jetpack features but actually needed none of the CSS. This is what was able to completely stop any Jetpack CSS for me (for functions.php, or functionality plugin): -->

// First, make sure Jetpack doesn't concatenate all its CSS
add_filter( 'jetpack_implode_frontend_css', '__return_false' );

// Then, remove each CSS file, one at a time
function jeherve_remove_all_jp_css() {
  wp_deregister_style( 'AtD_style' ); // After the Deadline
  wp_deregister_style( 'jetpack_likes' ); // Likes
  wp_deregister_style( 'jetpack_related-posts' ); //Related Posts
  wp_deregister_style( 'jetpack-carousel' ); // Carousel
  wp_deregister_style( 'grunion.css' ); // Grunion contact form
  wp_deregister_style( 'the-neverending-homepage' ); // Infinite Scroll
  wp_deregister_style( 'infinity-twentyten' ); // Infinite Scroll - Twentyten Theme
  wp_deregister_style( 'infinity-twentyeleven' ); // Infinite Scroll - Twentyeleven Theme
  wp_deregister_style( 'infinity-twentytwelve' ); // Infinite Scroll - Twentytwelve Theme
  wp_deregister_style( 'noticons' ); // Notes
  wp_deregister_style( 'post-by-email' ); // Post by Email
  wp_deregister_style( 'publicize' ); // Publicize
  wp_deregister_style( 'sharedaddy' ); // Sharedaddy
  wp_deregister_style( 'sharing' ); // Sharedaddy Sharing
  wp_deregister_style( 'stats_reports_css' ); // Stats
  wp_deregister_style( 'jetpack-widgets' ); // Widgets
  wp_deregister_style( 'jetpack-slideshow' ); // Slideshows
  wp_deregister_style( 'presentations' ); // Presentation shortcode
  wp_deregister_style( 'jetpack-subscriptions' ); // Subscriptions
  wp_deregister_style( 'tiled-gallery' ); // Tiled Galleries
  wp_deregister_style( 'widget-conditions' ); // Widget Visibility
  wp_deregister_style( 'jetpack_display_posts_widget' ); // Display Posts Widget
  wp_deregister_style( 'gravatar-profile-widget' ); // Gravatar Widget
  wp_deregister_style( 'widget-grid-and-list' ); // Top Posts widget
  wp_deregister_style( 'jetpack-widgets' ); // Widgets
}
add_action('wp_print_styles', 'jeherve_remove_all_jp_css' );

<!-- Thanks to Jon Bellah, TJ Kelly, George Stephanis, and everyone else who chimed in to help me. -->

<!-- I suspect this will change over time. It seems to me the best possible way to do this would be to serve a concatenated stylesheet for just the featured you have turned on, and have a single named thing you can deregister. -->