A company called Social Intelligence just gave you one more reason to beef up and clean up your online profile. This a professional service that, ". is a fully compliant consumer reporting agency (CRA) with processes and operations designed and operated in adherence with federal, state, and local employment laws as well as the Fair Credit Reporting Act (FCRA). Providing a user friendly portal to employers, our infrastructure enables the scalability, security, and dependability that an organization requires in its business practices."
That's legal-eze for yes, they can do that.
I predict this is the way of the future for background checks, and will be standard along with criminal background checks and drug screening. This type of service helps protect the employer (or prospective employer) from either inadvertent discrimination or the perception of discrimination based on factors that are currently illegal such as race, religion and gender.
It protects the employee by...well, actually, it doesn't protect the employee. The service is paid for by the employer (the prices aren't published, and are subject to negotiation), is run for the benefit of the employers who are looking for information to help them stay out of legal trouble while increasing the quality of their workforce.
This company searches up to seven years worth of social media presence, and will report anything that is normally considered inappropriate in the workforce - i.e., anything that could be considered disrespectful of other people based on race, religion, gender, etc.. The report will also include information about any illegal activities (even if written in jest), such as drug use or potential criminal activity.
For more information about what the company can and will check and report, check out the FAQ page. The crew at Gozmodo ran social media background checks on themselves using the service to see what would turn up. You can check out their results here (language alert). Also, Forbes and PCMag have more examples of the types of online activities that can reflect negatively on a job search.