An interesting comment from the mailing list:

"Aside from speaking whether 5112 lines of code is really a good sign, there is separate issue regarding quality. When you will look at claim that some language (lets take for example C# or Java) "supports feature X", that really means that the feature is supported. In D this for sure means that the feature is either broken or misdesigned (shared libraries, routine code breakages, obsolete ms32 object format, AA arrays, shared, const postblits, odd template crosstalk bugs, type system holes, segfaulting lambdas, unstable stdlib, absent of third-party libraries). Untill this stuff is fixed this is a huge barrier irrespective of whether D is used in Facebook or not."