Tinseltown is, as you might have guessed, a bit loopy for all things young, which forces performers to be a bit shrewd about revealing their age. A few years ago, a nameless actress sued IMDB for making her birthdate public, telling the world that she was "many years older than she looks." It's hoped that, by removing this information, working performers will be treated on their merits as an actor rather than as a birthdate. California official Ian Calderon is quoted by Deadline Hollywood that IMDB Pro's age data is information that "should not be part of the casting decision."
The law itself is pretty narrow and only appears to affect websites that deal with employment decision making. That includes IMDB Pro, which is used by casting agents to source talent, and other such online actors directories. What it doesn't cover, however, is news websites and information resources, so it looks as if you're still going to be able to use Wikipedia to learn George Clooney's birthdate (it's May 6th, 1961). Of course, the law is likely to face a number of legal challenges given that it essentially censors free speech, so it'll be interesting to see how those progress.
It's worth noting that the majority of people who are treated less like a person and more like a number are women. Gabrielle Carteris, the current president of actor's union SAG-AFTRA, was famously forced to lie about her age to appear on Beverly Hills, 90210. She auditioned (and won) the part of 16-year-old Andrea Zuckerman, despite being 29 at the time -- so clearly age is but a number, and one that casting directors would be well advised not to worry about.