We ship MediaWiki with a hitcounter feature. This feature basically makes an update to the database on every page view just to count how many people have viewed the page. And our default out-of-the-box settings have it enabled and set to 1 so that every single page view makes the most inefficient possible update.
Frankly I can't believe we ship MediaWiki with a feature of minimal use that reduces the wiki's performance.
This feature sounds perfect to split out into an extension for those who want it.