A survey by communications and PR firm Edelman shows many Americans don't trust either government or social media to handle their personal information. 35% don't trust the U. S. government, 34% don't trust Facebook, 32% don't trust Google and 28% don't trust Amazon.
While government spying on citizens is known, the extent of distrust in social media should be noted. Facebook in particular has had security and privacy issues. There is a "gender gap" with significantly more women than men trusting Facebook more than the government. (Judging by my personal experience, women are more apt to post on Facebook.)
Anyone with an email account has undoubtedly received at least one email today they did not expect and do not want. Some of them include attachments that may be dangerous to open. Your spam filter may catch some but not all of them. Be careful what you post, and don't assume your data is safe.