They have trouble all backing up at once.
Wargaming.net's flagship combat game, World of Tanks, has broken 40 million registered worldwide users today. That number easily has shattered their former record only back at May of 2011 of 3 million. Additionally, the record for most players on one server at any time has been broken by their Russian server, with over 500,000 at one time.
Putting it into perspective - last year League of Legends broke the record of 15 million reigstered, and that was before it extended into Asia. Forty million is quite a bit!
Julian "Mirai" Williams