When do you go public?

What I like most about writing a blog is that it provides all of us another venue for exchanging ideas.  So I am going to ask for your help and advice.
One of the many questions that Mike and I wrestle with is: When should a person with a mental illness reveal his disorder? 
Should he disclose it on a job application when he is seeking employment?
Should he bring it up during an interview for a job?
On a personal level, when Mike is dating, when should he — if ever — mention it?