Your theme's primary stylesheet is overriding sociable's stylesheet. Open up style.css in your theme folder and find this code, which is the culprit:
#content p,
#content .post ul li {
font: normal 13px/20px Verdana, Helvetica, Sans-serif;
margin-bottom: 10px;
margin-top: 10px;
color: #eaeaea;
margin-right: 140px;
text-align: justify;
}
This piece of code affects how unordered lists are displayed, and Sociable uses an unordered list to display the social media icons. Notice how it says margin-right: 140px. This is automatically adding a 140 pixel right margin to each list item (icon) in your post content.
Simply commenting out that line of code fixed the icon spacing problem, but I'm not sure if it would affect other parts of your site. You can give it a try (back up style.css if you're worried) and see if it adversely affects any other parts of your site.