Thanks for the thorough response Ryan.
I've changed the add-to links to onclick=setLocation(). It seems logical to separate the 'functional' elements of a website from the content elements.
I've read some differing opinions about the use of Javascript instead of HTML, with some people suggesting that Google is just as capable of reading Javascript syntax. Whilst I'm sure that's true, it seems like a pretty rational way of distinguishing between content and function, and I'm curious to know whether Google makes that distinction, and whether it's considered standard best-practice to separate your linking methods in this way...?