Managers--you've got to stop Googling candidates before you interview them.
Job seekers--you've got to stop accepting Facebook invitations when you interview for jobs.
For the managers who are hiring, what do you expect to find in a Google search? If you are worried about specific misconduct do a background check. Does it matter if they have pictures from a party last weekend, last year, or when they were in college? People who Google job seekers demonstrate that they don't have a good idea what they are looking for in a candidate.
Job Seekers--every social networking item you list on LinkedIn, Twitter etc. is fair game. Don't bash a company you interview with in your Twitter feed. Don't friend the person you interviewed with on Facebook. People who interview you shouldn't be looking there and you shouldn't allow them to see your profile.
This seems obvious, but seems like I read about more of these cases every week.