For example in #9518 we had a case where two scripts declare a Piwik and overwrite each other. In http://developer.piwik.org/guides/tracking-javascript-guide#multiple-piwik-trackers we explain how to use multiple trackers eg by calling

var piwikTracker = Piwik.getTracker(12,  "http://example.com/piwik/" );
piwikTracker.trackPageView();

However, creating the tracker instance is not trivial and is a bit different from the standard async tracker. For example a developer would need to make sure to call methods on the tracker in this order to configure the tracker:

['disableCookies', 'setTrackerUrl', 'setAPIUrl', 'setCookiePath', 'setCookieDomain', 'setDomains', 'setUserId', 'setSiteId', 'enableLinkTracking'];

Otherwise there might be side effects. Also one would have to change all calls to Piwik tracker from say _paq.push(['trackPageView]) to if (piwikTracker) piwikTracker.trackPageView(); etc. which can be a lot of effort.

I wonder if there are easier ways. Eg could we maybe also provide a _paq2, _paq3, _paq4, ...?
We probably don't want to pollute the namespace so maybe we could do something like _paq2 =_paq.create() or paq2 = _paqCreate();. This way one could create unlimited _paq instances manually as needed. All a developer has to do afterwards is to replace _paq with _paq2 and one is done. The order of the applied methods that are applied would be the same as usual etc.