I am interested to know what makes you believe they move quickly. Do you follow an internal blog or know engineers? From the items the two other people posted i

I am interested to know what makes you believe they move quickly. Do you follow an internal blog or know engineers? From the items the two other people posted it does seem that they post quite a bit but most of it seems to be about how facebook works internally or items their employees are doing for other people (AMAs). I'm not sure I agree with your second statement in this context but I do agree with it generally in the sense that it is harmful. Obviously if one never releases a product but runs through the rolling internal releases of redoing items they've already done, then that can lead to an terrible negative-feedback loop. For a company that is well-established, however, I'm not sure the same rules apply. You don't maintain success by iterating on your existing product offering and instead need to rely on either simplifying, speeding up or offering new products/features to your clients. One could argue that they are attempting to find alternative revenue source in these rewrites, which would be a valid argument and one I could understand, unfortunately I am not able to either confirm or quell that suggestion.