With the majority of Social Media systems having private messaging, a veto of this law is close to the equivalent of allowing an employer having the right to read all of the mail that is sent to your home. Does that seem like something anyone would be OK with? And the reasoning that it is a rare occurrence, and therefore does not warrant protection under the law is simply outrageous (also, the link shows the other reason for the veto was lack of funding for the Department of Labor to enforce the law, which seems to contradict the first line of reasoning). That sort of reasoning seems to be something that a bunch of lawyers, who also happen to make our laws, came up with as a means to allow future lawsuits as a source of income. 

To me, this is a pro-active bit of law making to afford privacy protections for a situation that has been happening and should require clarification for the general public.