Privacy laws

It has always been my understanding that privacy laws in the U.S. protected one and their personal information, such as census data and so forth, for 72 years; hence we can only look at the 1930 U.S. federal census today, but we will be able to see the 1940 federal census returns in 2012. (That's only six and a half years away and I already have a few key items that I need that census for, in order to verify genealogical theories.)

Today in my website searches for Michigan data, I ran across the Genesse County site that allows one to search the vital records index easily enough, but it claims to have marriage records from 1963. Maybe I'm a bit paranoid with all of the identity theft reports that been publicized recently, but wouldn't it be fairly easy to establish a new identity with this recent information available online? Just type in a few names ? Order a few key documents?

What are the parameters of the privacy laws in this arena?