I think the problem is that it's easier to get higher than you planned with edibles.
Yeah, dosage and lack of FDA oversight. I also worry about combining marijuana with the industrial food complex. Right now, marijuana is a local cottage industry that fuels small businesses. If the industrial food complex starts demanding marijuana concentrate for food products, marijuana will become another uncontrollable (almost) vice industry, like tobacco.
I'm worried that edibles could scuttle legalization. It's easier to overdose. Vapor is already safer than smoking. Sweets appeal to children. Industrial food polls low across all demographics. Many problems.
Edibles legally sold in Colorado (and the Netherlands) are labeled with dosage info and even sold in child protective containers:
Granted, the issue is that I have no idea how 25mg THC would affect me until I take it. But I had no idea when I first started drinking how an 8% beer vs. a 5% beer would affect me, or how many $2 long islands it takes to black out, or how many tequila shots I can handle before I throw up, etc. That's all a part of growing up, really.