The view.yml configuration and the use_stylesheet() helper allow a partial (or a component) to include a stylesheet or a javascript.
This is very useful for portlet-like components, who need to embed their own formatting and behaviors.
The problem is that the get_partial() helper just outputs the cached HTML code of the partial if found, without any consideration for included stylesheets.
branches/1.0/lib/helper/PartialHelper.php
Although it is properly done for actions without layout (where it's an object that is put in cache, not some HTML code), the cache doesn't work properly for partials and components.
A good workaround for JavaScripts? is to write a JavaScript include tag directly in the template, but doing the same for stylesheets is not XHTML compliant.