I mostly use localbitcoins for selling my bitcoins. They have not asked me about my personal details. But I don't know whether they bwould ask my details if I have to buy bitcoins.If they ask, then I would have to think about buying bitcoins with person face to face. Of course, all of us don't want to give or show too much information and we want to remain anonymous, if that is the case then maybe I agree that its better face to face when buying bitcoins