I'd be surprised if laced baked goods didn't become a real problem. Back in the late '60s, there were sickos out there who would bake marijuana into cookies, etc, served at parties and events where people brought food contributions. The situation was such that in some environments it was best to bring ones own food to eat and in the teaching environment to not have bake sales of home made treats.
Stoners may laugh. But it's a real issue for those who are drug free.
Urban legend.
It may have happened a few times, put it absolutely was not so prevalent that people needed to cancel bake sales. Despite what you think, most marijuana users are not stupid - neither are they sociopaths.
It defies logic to believe that someone would waste their perfectly good, and expensive, drugs, by giving them to people who do not want them.
If you think you are safe among friends, best be sure you know who your friends are.
Was anybody in Colorado unable to get pot when it was illegal?