How to solve the ever-growing core_url_rewrite table in Magento

Got an ever-growing core_url_rewrite  table in Magento? Don’t know what’s going on? I encountered this problem today: when I re-indexed my catalog URL’s, for some reason Magento added some extra rows. And it would keep on doing this each time I re-indexed it, when no product were even added, deleted or even modified. This was read further ...