There are a lot of applications now that could pose as a threat. Social networking sites are examples of such applications that could be harmful for you in the long run.
How much are you worth?
Do you know how much companies would pay for information? Even for just simple demographics, like gender, age, location and nationality? Stuff as simple as that, companies would pay millions just to have it. Imagine how much information we put on our profile sheets in social networks? We put in our schools, our hobbies, pretty much everything about ourselves. Such information can be used by companies to make marketing strategies; to check how much of the market they have penetrated; to see which demographic (such as social class, gender, school, age, etc) would be most likely to buy their products. Which demographics would they target their ads and their products to. Imagine how much they would earn in profit if they properly market their wares. Much much more that how much they'll pay for your information.
Sure, nothing's wrong with having targeted ads. It's how a company will earn money. It's just like TV ads, right? WRONG! Maybe it's just a little soft. No real damage is done, you'll also benefit by finding stuff that you want easily, but, would you really want these companies to know much information about you? Remember, people operate these companies. People in the company have access to your information. They can pull your record out, find out who you are, where you live, how to contact you, what your hobbies are, and worse, how you look like.
There's this app that I really find preposterous. It's an app (webapp) that let's you post information about where you are. Don't people see the dangers of letting the whole world know where you are? You could be feeding information to stalkers. And it's not limited to this webapp either. People use microblogs and social networks to post where they are at the precise moment. People can use this information against you. Companies could also put this to use. They can send targeted ads to you again. Since they know where you are, your phone or laptop can be bombarded with targeted ads. Like this shop is near you, etc.
You may be wondering why I keep on going back to companies that do targeted advertisments. Well, their the biggest threat. It's the most possible users (or rather, it's already happening) that will exploit your information. These marketing strategies are a little scary for me, because they'll know how to convince you to buy, to spend your money. You're thinking that you did that on your own. You decided to buy something, but in reality, these companies have conditioned your mind into buying.
A Way Out
I know what you're thinking. "I don't have that kind of threat because I only share information with my friends". That's a LIE. Unless you know all your followers on twitter, your friends in fb, 4sq, myspace, friendster, ym, tumblr, plurk, etc, which I doubt, you're not safe. You can't be so sure that your information isn't in jeopardy.
Of course, there's still a way around that ToS and PP, but it's still a way of safeguarding your info.
I hope y'all be more careful about your information.