"if you assume that a certain product in a bag with a picture on it is the same product as another bag with the same picture on it, that's exactly what we're talking about - a guess."
I agree that it's a situation you can't be completely sure in, but we who use do everything to make sure that it does not become a guess. Not having the information from a stamp thread makes it a guess and that's what makes not having information so dangerous. We need to stop thinking in absolutes such that someone said, "John said x bag is an 8, therefore, if I get x, I can expect it to be EXACTLY an 8". The rating tells me that someone, under disclosed situational variances (tolerance, usage history, ROA) thought these were stronger than usual; I will do less.
"...certain information was helpful more often than it was not helpful. that's a quantifiable metric but it's not at all clear to me how he could possibly measure it..."
Edit: Please don't link to something we don't currently allow. This is the second time. -phrozen.
You can see for yourself how consistent the ratings are. Additionally, the posters present ways to identify the knockoff bags and avoid them (Rihanna was a case of this)
And as for the FDA regulating food, we put waaaaaaaaay too much faith in authority because the things they "regulate" can make you sick and kill you...easily. We gain comfort from knowing something is regulated, but we don't always know what specific actions are being taken to ensure consumer safety and the actual feasibility of implementing those policies. Someone can easily poison a hamburger and give it to. It's just not in their best interest to do that. In fact, McDonald's uses the shittiest meat for hamburger filler and people eat it because they don't know (or don't care) it's in their food. Because that standard is established, other fast food places can do the same and consumers will think they have one option. Drug trade is the opposite: the informed consumer (demand side) truly does control the supply.
In "Food inc." it is shown that places known to have given multiple people e-coli will not always be shut down. I will agree that there is at least a route for accountability and discipline to be issued in the food industry.
Let's understand this together: part of the beauty of the drug trade is that it is one of the only truly free markets in a capitalist society. The rules of the free market are the authority and regulators of the drug trade. Stamps exist for a reason. Yes they can be forgeries; most often they are not. Regardless, if they are good, people will want them and the only way to sell a desired product, is to actually have it. The incentive to produce forgeries is not nearly as great because it hurts everyone: the user will not buy from the dealer, the dealer will not buy from the supplier.
This industry relies of repeat customers. Now, the free hand of the market is showing that it wants the information to know its product. People should want, and do want to know what they are injecting into their bodies. Though there is no way to be absolutely certain, any information is helpful because without it, we truly are just taking blind guesses and stabs (into the arm) in the dark.
Stamps have been around for a while, and in a multi million dollar industry that's as competitive as the heroin trade, they must serve a purpose and be more useful than not-useful. There will always be possibilities to lie about product quality or take advantage of the system, but in this truly free market, there is no reason to do this when you can make the most money selling the best stuff. Either way, knowing can only help this process, even if it isn't certain every time.