To give yourself a better experience, most chatting services allow you to filter your results. This happens rarely, but it is a possibility. However, if you know that your friends use the same chatting service, you may end up getting paired with them. The overall goal here is to meet new people, so you can’t previously know them. Yes, you are very likely to meet strangers while using chat rooms.
Will I Meet Strangers in These Video Chat Rooms?