A lot of people on these forums are not libertarians at all, except for on issues they benefit from....just like liberal republicans, who want small government only when it is a convenience to them.
An employer should be able to request access to your profile. This is no different than any other cost, such as a reduction in salary or benefits. When you look at a job, you compare costs and benefits ($50k salary, signing bonus, good experience, good location, vs. costs of long commute, lots of hours worked, have to share my facebook profile, etc)
Anybody here saying the government should be allowed to ban employers from asking for this information is no different than someone trying to get the government to implement minimum wage laws....and if anyone has taken economics they know how much minimum wage laws hurt, especially the poor. Go read Walter Williams. Ridiculous argument.