re: how many people do you know who have OD'd on heroin?

none, thankfully

I don't know any users that I'm aware of

I think both of the following can be true:

1) If you know a lot of people ODing or using heroin, you should reevaluate your situation. Maybe it can "happen" to anyone, but it usually doesn't, I suspect. It happens to people who are fricking around in ways they shouldn't be. Doesn't make those who don't better people, it just makes them wiser in one particular area (or wiser at some point).

2) That said, it can and does impact people you won't suspect. I don't think this is the majority or even a big minority, but it's possible and it's likely unwise to think you're insulated from it.