Talking Religion at Work - When is it acceptable?

Everyone says you're not supposed to talk about politics and religion but people generally talk politics at work or in other "off limits" settings.  I'm wondering why if someone mentions their faith at work (unless they're mentioning a holiday they're taking off) people immediately clam up and just nod their head? 

I realize it's not politically correct to get too specific about faith issues at work, but it seems strange to me.  If a person's faith/world belief is so central to who they are, wouldn't their views/beliefs be helpful to elucidate in certain settings in the workplace?  Perhaps an ethics discussion in HR in a gray area issue?  Or in discussing a client that has a religious focus to their organization?  I'm sure these types of talks may come up but you know what I mean. 

What do you think?  If people were to talk about their faith at work, what would be the best context and why?  Where would it be helpful and where would it hinder?

You can let me know here or email me at: johnhavens@blogtalkradio.com.

Oh, and please join our Facebook Group for the book.  We're getting a nice membership and would love to have your thoughts.

Best,
JCH