I say that there are people "in HR" who are not HR professionals. People think anyone can do the job. Wrong.
Actually a recent survey of SHRM members showed that fewer use social media to check up on candidates than previously and, if they do, it's usually just prior to offer if it's a tie or they are not sure. They cite concerns about being accused of discrimination, invasion of privacy, NLRA violations in addition to a lack of time. If one doesn't have time to do research on every candidate about to get an offer, they should not do it for any because the motive will be viewed as discriminatory intent.
As for the requirement of passwords, I had read about it and consider it a pure invasion of privacy. Again, there are lots of unprofessional HR people and people who work for unethical bosses and owners of companies (who are afraid/unwilling to cross them).
Heck, I got into a debate at our SHRM Leadership conference in November with HR people who said they refuse to even interview someone who has been unemployed! How does one know that, simply because an applicant is unemployed, they are unemployable? Perhaps they lost their job due to the economy and, simultaneously, an elderly parent became ill. So, they used the time to provide care. Refusing to even interview in that case is caregiver discrimination per the EEOC. Perhaps they or a family member were ill. Perhaps they relocated with a spouse. Perhaps there are a lot of legitimate reasons. But one would never know if they never even give them a chance.