Holy christ you're right. There are whole communities online of amateurs that publish their own 'adult' photos. What's the likelihood that they also post their family/other photos elsewhere online?
Pivot.
I assume most places like that would strip exif data already.
Imgur does, for instance.
In my opinion, personal blogs are a bigger problem. Even wordpress.com does not sanitize pictures. I believe many bloggers are unaware of that.
They should watch out anyway. This isn't anything that 4chan could theoretically do (although it now has become a lot easier)
4chan retains exif data afaik
Thats what they want you to think
People should strip it themselves (no pun intended)