1) Legality Issues
Always be aware of whether or not what you're sharing is legal. For instance, if you purchase private label rights articles, is it okay to share them with just anyone? How about your virtual assistant or writer? Can you share them with your best friend, since you purchased it and it's your best friend? If you understand what is legal to share, and what is not legal, you can avoid a lot of problems.
Remember when this happened? http://www.foxnews.com/story/2003/09/09/12-year-old-sued-for-music-downloading/
2) Security Risks
If you don't know where the file came from, it can be dangerous to send it on to a friend. This is how viruses and worms are spread throughout the internet. In addition, if you are giving someone else access to a file that resides on your computer, through a system like Dropbox or other file sharing program and they put a virus on it, what might happen to your computer or theirs? If you have downloaded the file sharing software to your desktop and you're not just accessing through the cloud, the automatic update feature is adding that file to your computer too.
3) Protect Sensitive Information
Thankfully, there are security features you can put into place that helps restrict the locations to which files can be placed, and to which others have access. This can help you protect sensitive information from others. Ensure that everyone you work with and share files with understands the risks and doesn't freely give out their passwords to shared files without permission.
4) Train Your Contractors
It's likely that if you have contractors, they have access to a boatload of personal information in your files. Not only should you check the background of your contractors before allowing them to have this information, you should also train your contractors about password safety, issues with file sharing, and copyright laws. If you don't want to provide training, at least test their knowledge on these issues prior to signing a contract.
5) Create a File Sharing Policy
Every business needs to have a file sharing policy that includes the accepted ways to share files, which files can be shared, with whom, and the procedure to follow should something go wrong. By both working toward the prevention of problems, and dealing with them should they occur, you can protect your business from legal issues and security risks.
Peer-to-peer file sharing is going to continue. Today you can share files easily via social media, email, file sharing programs and more. As it's not going away, you may as well develop a way to ensure that nothing goes wrong while engaging in peer-to-peer sharing.