wsperuzzi: If you check the Readme, you'll find instructions for manually inserting the Share This link in your template, rather than having Share This do it for you automatically. If you do that, and only put the link code in your template where you woud like it to appear (e.g., single.php) and not where you don't want it (e.g., page.php), you'll be all set.
It's actually pretty straightforward to do, because the plugin relies on just one substantive capability provided by the prototype.js library: Position.cumulativeOffset, which allows the plugin to position the expanded form in the correct place over the top of your page content. If you nuke that line in share-this.php, set the form.style.left and form.style.top each to 0, change the CSS for akst_form to position:relative from position:absolute, and remove the pesky lines that load the prototype.js library in the first place, you're almost there. The final 2 steps are just to replace all instances of the $() function with document.getElementById() instead and make sure you've manually inserted the form contents right below your form link in your theme (rather than, say, putting the form contents in the footer).
What's the outcome of all that?
First, the form now appears and disappears from within your page content when you open and close it, rather than appearing over the top of your page content. Second, your visitors don't have to wait for a 55K library to load in addition to your page content just on the outside chance they might click on the Share This link.
You can see it in action in the blog section of my mental health information site.
I wonder whether Alex would consider adding a simple user-configurable boolean at the start of the code so that those who want the extra 55K overhead can choose to do so, while those who would rather avoid it can switch it off without manually editing the code?
All the best,