I think it is a case of each to their own on this one (and many others).

Most of the warnings (ham, deli meats, soft cheeses etc) have to do with the risk of contracting listeria, which is very low. However, if you do contract it (from what I know) and get listerosis it is almost certain that your baby will get it which means the end of the pregnancy...

Personally, I have decided to take the better safe than sorry approach... Yes I love ham and deli meats and will have them on a pizza where I know they have been exposed to very high heats, but not in a toasted sandwich where they are usually only warmed up. The reason why deli meats are considered unsafe is that they are typically smoked rather than cooked which means they haven't been exposed to high enough heat to kill the germs.

I'm also really careful with mayonaise, eating salads when I'm out, making sure meat is cooked till there is no pink left and won't eat shell fish, cold meats, or sushi rolls (partly because of the rice thing, but also because they handle so much raw fish that the risk for cross contamination is really high).

I also haven't had any alcohol since I've been pregnant which is another one of these grey areas. For me, it's only 9 months of my life and if me going without means that I eliminate a risk (even a very small one) of harming my baby it's worth it. But I have also had a few people (mostly older women) patronise me for being so careful because the risks are so low. At the end of the day I think we all just need to do what feels right for us and not judge others for their choices...