Gen has captured the cost of monoculture with his excellent look at the unfortunate result of some technology choices made in South Korea years ago:
This nation is also a unique monoculture where 99.9% of all the computer users are on Microsoft Windows. This nation is a place where Apple Macintosh users cannot bank online, make any purchases online, or interact with any of the nation's e-government sites online. In fact, Linux users, Mozilla Firefox users and Opera users are also banned from any of these types of transactions because all encrypted communications online in this nation must be done with Active X controls.
Where is this nation?
The constraints on web culture in South Korea are a result of the adoption of SEED, an essentially proprietary cryptographic cipher mandated by the Korean government. The Wikipedia page, in typical geek fashion, describes the technology but not its social implications. The official page for the technology, in typical governmental fashion, has a skin of friendliness tautly stretched over an underlying hostility.