Their primary role in page design is to distinguish among the various elements on a page, so they should only be used when a distinction needs to be made. And remember that judiciously placed white space can accomplish the same goal, without adding visual clutter to a page. The myriad rules, screens, and boxes on this newsletter page are intended to clarify its content, but they just create clutter and confusion. Always give a page a place for the reader's eye to focus, and a path for the reader to follow through the page. Use contrast and careful positioning of page elements to guide the reader.
Consistency demonstrates a respect for the document and the reader.
In the end, legibility never goes out of style.