Some people say they do, or feel that they do, but I don't think it can be true love. Love is about far more than just getting along with someone and having things in common. Love is about knowing a person and accepting that they have minor faults. Love is knowing that they'll be pleased to see you at the end of the day even if you've had a terrible day and have un-brushed hair, no makeup, and you're still in your pyjamas. Love is about trust and respect, and actions speak louder than words here. And love is knowing that you are just as happy in each others company whether there is talk or silence. None of these things can be found just by talking to someone. When you meet someone in a chat room you may fall in love with the person that you THINK they are, or you may trun them into your ideal person and fall in love with that. But you cannot truly love someone until you have spent time with them, seen their expressions, watched how they handle certain circumstances, had good days and bad days together, and learned to be comfortable in each others company.
They may meet in a chatroom and then marry, but I doubt that many of those marriages last.