The Javascript tracking code has a fixed URL in two places. The first being the pkBaseURL and in the second in the <img src=" at the bottom of the code.
This means that 3rd parties can discover other websites you own. As such, its a major problem for people and oranisations who wish to keep their Internet businesses private.
Is there an alternative or a modification that can be made to the tracking code, so the URL can be hidden?
the tracking code needs to know about the url its loading from / posting to.
You could just run piwik on the same domain as the domain you are tracking.