Counting outgoing clicks.

[eluser]Michael Wales[/eluser]
Most of the JS libraries aren't that large, but you could always code it up yourself in JavaScript.

Personally, I would use a library as it allows you to use CSS/XPath selectors, so it's not in-line JavaScript (which we call obtrusive) as well as handling all of the browser compatibility (like how IE and Firefox handle HTTP Requests differently).