Social security cards can be laminated, but it's not advisable to do so. Lamination can interfere with security features on the card, which may result in employers and others not accepting it as a form of identification.
A requirement of the Social Security Act is the creation of identification cards that can't be recreated for counterfeit purposes. The Social Security Administration is continuously adopting new technologies and methods to fight fraud, and altering a Social Security card could interfere with those safeguards. According to the SSA, laminating a social security card could impact a person's ability to gain employment or access certain nongovernment benefits that the card might otherwise make possible.