Round table: Have you ever unknowingly made an insensitive remark?

We were discussing this in the office today - those times where you might have made a light comment on something that actually was a very sore point for the person you were speaking to, or when you had an opinion on something, not realizing how very personal it was to someone in your audience.

For example: I recently discovered that someone I knew lost a child who committed suicide by jumping off the Golden Gate Bridge. While the topic of suicides on the GGB is not something I ever discussed with her, it is definitely something where I've talked about the issue in a very theoretical and removed way. (There are debates about what to do about the high number of suicides off the bridge), and while those are fine, it would be absolutely cruel to make one of those comments to her. Literally, just the thought of how easy it would have been to be so unknowingly cruel takes my breath away. 

This happens a lot - I have heard plenty of horror stories of the thoughtlessly cruel things people have said to women who have suffered miscarriages (without knowing that they have). 

And it's very easy here in a place like CC, where we might debate topics that cut much closer to some users than others. 

Have you ever unknowingly made an insensitive remark? How did you handle it? Is it different online than in person?