Th is week Facebook will register its 500 millionth member. It's a milestone both significant and meaningless: yes, it's a reminder of just how big the social-media giant has become, but really—did we need reminding? That Facebook is a part of many Americans' daily lives is clear.  But how it's affecting those lives is still being examined. We know that Facebook can be good for your health, and that it can make everything from networking to sharing photos easier. But there's also a potentially sinister side, even aside from dubious privacy issues. Below, 10 ways that Facebook can do more harm than good.

1. You'll be reunited with your biological parents. This can be good news, but it's not always. Take Prince Sagala, who found her biological children on Facebook—children she alleges were kidnapped more than a decade ago by her ex-husband. The mom and kids are now reunited. The only problem: the kids grew up with their dad and don't want anything to do with the parent who now has custody. And in an even more horrifying story, Aimee Sword was sentenced to nine to 30 years in prison recently for sexually abusing her 15-year-old biological son, whom she tracked down on Facebook. 

2. Your creditors can track you down. Creditors use Facebook as a way to both track the movements of debtors and keep their eyes on any potential assets that could be seized to cover those debts. At first, lenders may use Facebook to determine whether you're a worthy candidate for a loan. But should you come to owe a creditor money, the company can track you down and discover your assets by monitoring your Facebook feed.  

3. Your insurers can deny your claims. Remember the woman who was receiving workers' compensation for depression, only to be "outed" by Facebook pictures of her smiling? Her insurance benefits were cut off, with insurers saying that her photos showed she was ready to return to work. That's left attorneys who argue for disability benefits concerned. Many now advise against giving away too much on Facebook. 

4. Your ex can use it against you in a divorce. Facebook is a popular tool for divorce attorneys, who comb pages of their clients' spouses for evidence of neglect, infidelity, or deception. (One study suggests that Facebook comes up in one out of five new divorce petitions). Mashable says a woman lost custody of her children after her ex proved she was spending time tending her crops on Farmville instead of spending quality time with her kids, while divorce lawyers have given multiple interviews extolling the site's virtues as a way to air damaging dirty laundry. 

Read Part II here.