I got a few friendship requests from people I don't know.Is it by mistake people get these friendship requests? automatically sometimes Facebook app makes these mistakes?
They may be friends of your friends. I don`t think it`s by mistake. I also get many from unknown. But I check whether they are friends of my friends or not. Some times I delete, sometimes accept depending on their profile.
Friend's suggestions, common categories like place, friends, workspace,new account etc., can get your fb account details for adding. In addition yours likes,shares and comments may be liked by them so they might have sent