Call A Public Script From A Domain Securely?

I want to call a script from one domain in another domain. How can I *guarantee* that the page calling the script is from my domain and not some hacker/malicious user?The context is that I'm writing my own commenting system, like disqus or intensedebate. They use javascript to imbed your comments (stored on their site) in your site.

Here's how intensedebate's "generic" approach works: You imbed this code into your page:

Code:

<script>
var idcomments_acct = 'YOUR ACCOUNT ID';
var idcomments_post_id;

[code].....

The problem is that anyone has access to your accound ID by just looking at the HTML source, so anyone can bomb your account...