  I'm famous for not baby proofing my home. I chose early on to not go out of my way to rearrange my home for my kids. However, I did take care of things that could kill or mame like sharp objects, anchoring bookshelves, etc.
I found out that bleach is the top reason people call poison control, and since I've found that veniger can do almost anything bleach can and then some, I stopped using bleach. Today I came across urlLink this article that goes over common drugs in the home that are surprisingly toxic to babies and toddlers. In my experience, your own home is not nearly so dangerous as those of others. You know your own home, which parts are the most dangerous, which parts to keep your kids out of.
You don't know those things about the homes of others. My parents aren't used to having kids in their homes at all, as a result their medicine cabinet is at floor level. I'm sure it contains many of the drugs in that article. Their cleaners are all toxic in nature and located under their kitchen sink. This is just one example. You never know if other people's homes have guns or other dangers, even if they are parents themselves.
Maybe your only recourse for this is to teach your kids not to explore other people's homes, but rather respect their space. This is so anti-attachment parenting, I know. You don't want to be paranoid, but you want to be realistic about dangers. 
