Do internet companies such as Facebook or Google use MongoDB despite the AGPL license?

Disclaimer: IANAL, and seeing this from a non-US standpoint, so take this with a grain of salt. I would guess that most companies will not be modifying the server, which is the part covered by the AGPL (Tokuteks's case is obviously atypical). So if they do not add anything to the server, they do not have anything to redistribute about it. Regarding drivers, the wording in the FAQ is very peculiar: /supported/ drivers are released under the APL2, while the official Go driver is released under Simplified BSD, but guess what: it is not /supported/. However, I see nothing requiring alternative drivers to be thus licensed. The GPL part of the AGPL is not at issue here, since drivers are not linked to the server. The additional requirement of the AGPL is to distribute AGPL code providing a service over a network. For the drivers to be contaminated by this clause, they would have to not only use the AGPL code over the network, like a driver does, but also include AGPL code, which would be an obvious temptation for a C++ driver, to leverage parts of the server code like BSON serialization, or even just the headers. Barring this case, drivers are typically not linking/embedding AGPL code and should therefore be licensed under whatever other licensing requirements may apply. Not saying anything about other kinds of potential IP issues, likes patents or trademarks. Finally,  the AGPL is only one of the two ways a company can use MongoDB: most usage beyond development and very early stage startups will be using the software under the commercial license, which carries a cost (and brings extra features and services), but does not impose any redistribution clause.