Personally, I'm not a security expert. I've worked in web for near 20 years, on some reasonably large network projects so I've picked up things here and there, but I still defer to our actual security experts when we roll things out

That said, I'm not 100% convinced I could set up a webcam streaming online without accidentally exposing it to the wider internet. Maybe 95% sure? But if even I couldn't guarantee it, what chance does your average joe who mostly only uses his computer for netflix have?