Maybe a rant, but well deserved too. There's a fairly large thread in DIY recently about diactyl, acetoin, ap (dikotines? forgive my spelling on these) appearing in flavors not suspected of them, fruits, nuts, maple, etc. Started writing to vendors and even some admitted to it. Yet there are BIG eliquid manufacturers saying they don't have them in their juices. They are not independently testing. A few who are testing have at times pulled eliquids from sale. It's not just those 3 ingredients (and the debate for/against them isn't close to settled) but it's other containments. They should have some testing protocal. They also need a resident chemist. They also need a food grade work facility and adhere to local health laws, esp if they claim they make their own extractions, nets etc.
There's a conflict of standards from the beginning; flavoring companies only test to 95% and it's the remaning 5% that is found to have contanimation/undesired ingredients (sorta like cereal is allowed to have 1% insect parts). At the same time I was impressed with some of the major flavoring companies stepping up to the plate with retesting to a 99% level of all their flavorings even though they don't have to. TFA, FW, FA and Capella responded. (Capella has a new custard with none of the 3 above in beta testing now). FW is still testing and reported 3 flavors with diketones (whatever) in them but the amounts (ppm) was quite low (under 1%) and they are reworking them. It's pretty well known some eliquid manufacturers use what flavors and they are making the claims they know are false / never asked the flavor manufacturer / shouldn't sell without testing themselves.
This is a nitpicky example over probably not the biggest risk out there. It's just the only example that has hard data on the processes behind manufacturing flavors and mixing eliquids. The vendors reporting on this example are the ones do have high enough standards that they can even give a report. Most can't.
And that's why this needs to be taken in context. People have been mixing flavors and eliquids for several years now and I've heard of few incidents. Never a report that has caused serious or permanent illness / damage etc. like foods / pharmecuticals can; ecoli, salmonilla type nasties or do the harm smoking does. It's still no guarentee of safety or the way to grow an industry.
Allergies are growing for every substance. I don't think that's particular to eliquids.
Yup. There's a lot of people who say their coworkers and friends like what they mix and so they start selling it. I doubt if many of their kitchens would pass a health inspection for commercial use. Does someone mixing in the back of a b&m wash their hands after they wipe their nose? McDonald's can't even ensure that, but at least it's a standard. I'm all for complying with local health standards at the minimum.
Over half the comments in the 100% VG threads think "organic", "natural" and "synthetic" applies to combining chemical molecules. It is impossible for any eliquid to be "organic" (as in certified) anyway. How many times do you read "organic" being used? Many seem unaware that many flavorings have PG in them. I don't like to think about it.
I think what disturbs me most is the most is expensive, premium eliquids (like those in the Zample Box) are the most secretive about what their liquids contain. It's a marketing tool to charge a higher price for their "propietary" ingredients and that makes them "PREMIUM" line (ha-ha). But I'm actually more disappointed in the average vaper that consider that's acceptable practice since one of my biggest concerns about major corporations in this field stems from slippping in secret ingrediants that have made cigarettes more addictive without raising nicotine content. You can bet your bottom dollar they intend to do the same with eliquids.
Even that greek, good guy doctor is saying eliquid NEEDS to be more addictive than cigarettes for ecigs to work. Njoy admitted working on the same for their liquids in the interview with NYT a few months back. Ugh. Last thing I want are more secret chemicals / nanoparticle bs in my lungs. That is the more likely future. Give me the unknown kitchen vape.
Enough of my rant too. It's basically meaningless.
Ok maybe a rant coming maybe not

The industry is being saturated with juice vendors. Ok that's usually good for the consumer when a market becomes more competitive but in this case I fear it's not. Too many people are just jumping into an open market with little or no experience both as a business person and as a manufacturer. They do little or no research and quality control. I'm all for mom and pop business however it seems to me if your going to do something you should do it right. With so many new vapers we are seeing more and more allergic reactions and side effects. I was shocked to see vendors selling juice with diacetyl and even more shocked they had no idea what it is. That whole thing came out in 2010. Plus some are using essential oils and oil based flavorings etc. Not to mention there's food grade vs pharma grade vg and pg. (Pharma grade is used in inhalers and prescription items) guess which costs more

yeah you can buy gallons of pg at feed stores and vg at candle and hobby supply stores. Would I inhale it? Nope!
Just because you can eat or ingest it doesn't make it safe to inhale. Try inhaling a Big Mac and let me know how that works out for you

also things need to be sanitized. Your inhaling it not eating it. Bacteria contamination that wouldn't make it past stomach acid will thrive in your lungs. I sometimes just get a mental image of a barefoot hillbilly mixing juice in his bathtub
Ok I can ramble all day but you get the gist of it. Do your research and ask the vendor for disclosure on ingredients, mixing procedures, sanitation, etc BEFORE you jump on the 150ml for 12 cents deal.
Just my