1. Boundaries are Thin at Best
Many people still believe that their Facebook page, Twitter feed, and websites used for personal use are off limits when it comes to impacting your professional life. This is clearly no longer the case. In fact most recruiters Google you before they ever read through your resume. Whatever is public and online is fair game for people to use when they make decisions about you.
2. You Can Build Some Boundaries
Recently I gave a talk to a group of rising college seniors at the Jack Kent Cooke Foundation and this question came up: "Should you be friends with your boss on Facebook, etc.?". The answer is it is up to you, but clearly you mitigate risk to some degree if you create boundaries to separate your personal and professional life. Connecting with professionals on LinkedIn makes perfect sense, other channels can create problems depending on what you are sharing.