history:Mongo > db.test2.update({$and : [{"_id.coid" : "testcoid"}, {"communications.sid" : "testsid"}]},{ $push : {"communications.$.clicks" : {$each : ["www.google.com" , "www.facebook.com"]}}})
history:Mongo > db.test2.findOne()
{
    "_id" : {
        "coid" : "testcoid",
        "cid" : "testcid"
    },
    "communications" : [
        {
            "campid" : "testcampid",
            "clicks" : [
                "www.google.com",
                "www.facebook.com"
            ],
            "sid" : "testsid"
        }
    ]
}

history:Mongo > db.version()
2.4.1