How good is registration through social networks in contrast to local users?
Let's start with the fact that a one-time mailbox is not a problem at all, there are a lot of resources. And that's why spammers fall asleep more advanced sites with links to any nonsense type, look how it's interesting.
Almost in all known social networks registration without a mobile phone number is impossible, agree that to buy sim cards for this every time no one will.
I am sometimes asked a question - after all, not everyone has a social network?
Well, in this case, a person sitting at a computer in 99% has a normal email and phone. If he needs to write so much, I think he will be able to have at least one social network.
And if he has mail on Gmail, then in fact, and do not need to, he is already in the social network Google plus
What else can you save from spam if you need guest records on the site?
Of course, premoderation of messages is when you as a resource owner are notified and decide to activate a guest record or delete.
Login to the site through social networks protects from spam and junk :)