With the iPhone 3.0 firmware, Apple upped the max number of app pages on the iPhone from 9 to 11. Theoretically, that increased the number of apps the iPhone could support to 180. Theoretically.
iPhone site appadvice has both rationalized and confirmed that even though you can't see more than 180 apps in the iPhone's menus, the iPhone can support as many apps as it can store. How? Spotlight. It's common sense when you think about it. You can search basically everything on the phone with Spotlight, even content not on the menu. So of course you can search additional apps.