I see comments like this coming up on Hacker News almost every month and I tend to think that people who make these comments are either too young and/or have not worked for a mid-sized to a large company.

If you have worked in any company that deals with internet-facing traffic serving the size of audience that Twitter does, it should be obvious that 1k employees is nothing if you want to have all the necessary teams you need to keep the business running, for example, software engineering, software support, hardware engineering, hardware support, network engineering, software engineering, HR, finance, legal, PR, management, IT department, etc.

A company of this scale is not just code and raw technical skills. There are many nuances that you need to appreciate before you understand why it involves 1k-5k employees.