Since their service is free to users and they primarily generate revenue by ineffectively advertising to people who simply want to connect socially, I wouldn't say Facebook is a very sound investment. It is a battle between the users who want privacy and the companies who want user data, where the outcome could be that FB loses a ton of users or FB loses a ton of funding. FB also seems to have a lot of debt, which could hinder growth considerably since they don't have a ton of ways to make money or increase their customer base in the first place.