Well actually it might have a way guys

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Someone above said even with all botnet of the world, it can't take down Facebook. Well i doupt about that first. DDOS is simultaneous connection, so even if they have 500 millions members or even 1 billion, there are 500 millions zombies computers too.
If those 500 millions goes to facebook, i seriously doupt that facebook has an infrastructure to hold them all together at the very same time.
Do Anonymous has such power, nope ofc...
DDOS is a combinaison of simultaneous connection as mentionned above so this is fixed number. But what if you increase the power of each single connection, to take down with a lower number of machines ?
Recently, an old exploit kicked in with SSL which cause an infinite loop asking for the certificate, it is more ressourceful and some people say with one land internet connection you can take down a server with a tool. I won't give the link of it but it is publicly released...
I don't think facebook has millions of servers