Used addresses for previous business
Your address where you are planning to send coins to has been used for previous business, where your business partner can track all additional transactions. Always check twice, if your address has been used for previous business and for what business exactly. To keep your privacy, never use and mix addresses from previous business
Address has been public
Your address where you are planning to send coins to has been posted publicly on an internet site. If your address where you are planning to send coins to has been posted publicly on an internet site, you need to consider your privacy to be somehow compromised and affected negatively, as more conclusions about your transactions can be drawn publicly, for example tied to a social media account or your Bitcointalk account.
Whenever I read about this, I consider that most of us on this forum are guilty of this. We use the same addresses when applying for signature campaign and also our bitcoin addresses has been public. Also, it will make no sense to keep changing bitcoin addresses every other week by sending a PM to the signature campaign manager. What do you say about this. We are vulnerable and exposed.