Try the search feature in many CMS systems. Those tend to really suck, with WordPress' being awkward enough that a whole ecosystem of plugins cropped up to replace it.
There's also at least one version of the OpenCart admin search which was designed so poorly that it didn't actually search based on whether the term was anywhere in the page title/content, but whether the title started with the search term (I think they'd screwed up the MySQL syntax). That was interesting.
Either way, search on a system not designed as a search engine is usually okay at best, absolutely terrible at worst.
