[{social:{ok:"12345"}},{social:{ok:"56544"}},{social:{vk:"345645"}},{social:{vk:"65453434"}},{social:{vk:"3422324"}},{social:{google:"645645456"}},{no_social:"2312341423"},]

db.collection.aggregate([{$group:{_id:null,vk:{$sum:{$cond:[{$gt:["$social.vk",null]},1,0]}},ok:{$sum:{$cond:[{$gt:["$social.ok",null]},1,0]}},google:{$sum:{$cond:[{$gt:["$social.google",null]},1,0]}},oneclick:{$sum:{$cond:[{$lte:["$social",null]},1,0]}},}}])