0. Premature optimisation is the root of all evil 1. Approximately zero big sites use ruby 2. Of large sites, very few would actually care that much about tiny on-wire messaging optimisation since other elements are far more significant to bandwidth use. 3. On-wire messaging in binary destroys transparency, which means PITA debugging and wasted programmer and API-using developer time. Programmer time is far more important than computer time or a few bytes of bandwidth in most developed nations. 4. You have to pay for the binary serialisation with additional client-side code, which means you've actually gone backwards until you've communicated enough that the delta between JSON and binary format message sizes have outgrown this initial load time penalty. 5. Initial load time penalties are often more important than subsequent use, since generally this is the only time client bandwidth (the only side of the bandwidth equation relevant to performance in 99.99% of cases) is going to be challenged to any serious level. 6. Refer to point zero.