I'm using 7.11. I messed with it a while and couldn't get it like I wanted the way it was scripted so I just use a major hack.
I changed the first table entry in sys_objects_social_sharing to the following code and deleted the other table entries:
<span><iframe src="//www.facebook.com/plugins/like.php?href={url_encoded}&send=false&layout=button_count&width=450&show_faces=false&action=like&colorscheme=light&font&height=21&locale={locale}" scrolling="no" frameborder="0" style="border:none; overflow:hidden; width:100px; height:21px;" allowTransparency="true"></iframe></span>
<span>
<iframe allowtransparency="true" frameborder="0" scrolling="no" src="//platform.twitter.com/widgets/tweet_button.html?url={url_encoded}&text={title_encoded}&size=medium&count=horizontal&lang={lang}" style="width:100px;height:21px;"></iframe>
</span>
<span width:100px; class="g-plusone" data-size="medium" data-href="{url}"></span>
<span>
<a href="http://pinterest.com/pin/create/button/?url={url_encoded}&media={img_url_encoded}&description={title_encoded}" class="pin-it-button" count-layout="horizontal"><img border="0" src="//assets.pinterest.com/images/PinExt.png" title="Pin It" /></a>
</span>
<script type="text/javascript" src="//assets.pinterest.com/js/pinit.js"></script>
<script type="text/javascript">
window.___gcfg = {lang: '{lang}'};
(function() {
var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
po.src = 'https://apis.google.com/js/plusone.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
})();
</script>
Now everything is horizontal to my liking. DISCLAIMER: I do not know if the format will change should site visitors start using the social buttons. Since this is not a public site, I don't have a good way to test what it's like to have multiple participants. Hopefully all attributes but the actual counts of people using the buttons are turned off. I never have used a Pintrest button.
I'm sure someone more experienced in css formats will have a much graceful solution working with the general and default css files. Goodluck!