For example, if an employer sees on Facebook that someone is a member of a protected group (e.g. over a certain age, etc.) that employer may open themselves up to claims of discrimination if they don't hire that person.

CNN: Doug Gross,

In both countries, the percentage of people with an E-2 is about twice as high in the 100-plus age group as in the general population.

WSJ: A Gene Gives a Hint Of How Long a Person Might Hope to Live