[dredge]

I will hazard a guess that people were using it to 'spin' content for SEO purposes, by automatically translating others' content to foreign languages and back again.

If so, I imagine the double resource drain of doing that and then Googlebot indexing all that useless content would be a compelling reason to turn it off.

[cuchoperl]

Also, its difficult to monetize the API, for example, with ads.