By the objects of our affection being attractive and likeable!
As golden411 said, one of the downsides of social media. But in reality, there have always been stalkers in all sorts of random areas of life. One of the first female astronauts had a stalker for instance, a fellow astronaut wrote in his biography about getting a panicked call from her because he manged to find where she lived. And that was long before social media - working for an organization that should have some clue how to deal with publicity. So really social media is just changing it and making it more visible. Maybe seeing the behavior will help some young fans click sooner where the line is between fan and inappropriate. Maybe seeing it will help some people see see it as creepy, or maybe it will be like celebrity sex tapes and agents will want them, who the heck knows.
I find it interesting to observe to be honest. How much do you share? When do you share it? Where is the line between marketing yourself and being too available? How do you tell the difference between the weirdos you should humor and the ones that can be dangerous? These are questions that skaters and similar have to deal with and are dealing with as the very nature of social media evolve. No one can know the right answer, because everything is still developing. Frankly where all this goes is endlessly fascinating to me. How do you get fans and keep them, without some turning into stalkers? Where is the line?
At any rate, I do view it as an unfolding media case study that I am watching with interest. I hope that our skaters never have to deal with anything beyond mild annoyances, that bemuse more than scare them. But I also hope they talk a bit about the choices and policies someday in their biographies.