This sounds like an excellent idea for those looking to reduce the amount of alcohol (or other drinks) they consume. Do you have any suggestions for the agent used to make the drink taste bad? Generally speaking, sour or bitter tasting agents are used to deter people from things and in some cases even spice. I personally had a bad habit of biting my nails and have used bitter agents on my fingers to deter me from doing so.
A couple of potential pitfalls did spring to mind here though. Firstly, I think that beverage companies around the world would be fighting pretty hard to ensure that the taste of their drinks are not tarnished with foul-tasting agents. I know that there are several rules in pubs and bars as to how drinks are served, but I guess as long as the agent is added by yourself then this shouldn't be too much of a problem. Secondly, when I have a pint, I know that the last moutful never tastes as good as the first one (due to the carbonation release, temperature and freshness). Because of this, it is not uncommon to see people leave the last part of their drink in the glass and move onto a fresh one. I could definitely see people trying their best to avoid that final, less than tasty mouthful!
Adding agents to drinks in public is also something that has become a bit of a hot topic due to the prevalence of date-rape drugs. Pubs and bars would be very wary of these sorts of things happening and may look to enforce rules where adding things to drinks is highly frowned upon. This leads me to the conclusion that this idea is probably best suited to at-home drinking. It can be used for alcohol and other drinks such as coffee or sodas that can become addictive, and I definitely think this could be useful.
Going back to my bad habit of biting my nails, over time I actually found that I didn't find the bitter taste as bad as I did when I first started using it. This could be due to the fact that my taste buds had changed due to exposure to the agent or maybe I just realised it wasn't so bad after a while. Taste buds can change over time and so do you think there is scope for different flavours and/or intensities depending on what you are drinking and how much you want to stop? A bitter agent, for example, wouldn't show up so well in a pint of bitter and certainly wouldn't deter someone who enjoys bitter drinks.
Is there also potential here for weaning kids off certain drinks such as milk? Just an idea.