How Secret is Your Secret?

Emily Cale isn't my real name. I write under a pen name for a variety of reason, most importantly protecting my career. 
Recently my husband and I were discussing it and he pointed out how easy it would be for someone to figure out who I really am if they wanted to. If you put all the bit and pieces of my life that I share together and put some serious effort into Googling, you'd probably be able to come up with my real name. 
Buy why would you want to? Trust me, my online and book writing life is far more interesting than what I really do. That doesn't mean that someone somewhere might not eventually feel differently. 
Or someone who knows me in real life might happen across my blog and figure out that we are actually the same person. 
So that leads me to my question(s).
How secretive are you with your pen name and writing life?
Why? (What do you think you would lose?)
Any thoughts are much appreciated.