Regulation is a bad idea in every single case. It makes the people blind to values and makes people complacent with the idea of a nanny state, where all hard decisions are made by the authorities on the individuals' behalf. I, for one, wish to retain as much of my individual liberties as possible.
This additional measure does nothing to discourage smoking - all smokers know that their habit has a high likelihood of causing cancer, heart disease, and other complications if they don't quit. Have you ever met a smoker that believed their habit is healthy? It's a pointless waste of ink and bureaucratic ineffectiveness.
Cigarettes are extremely bad for you, and I think it is important for the packaging to explain that. Some people might not be taught that cigarettes cause lung cancer, and I think this should be clear. Also, I think this is important for cigarette companies so that people don't sue them after they get cancer.
I don't see any purpose for cigarettes being sold in plain packages. They contain warnings, which is sufficient enough to deter people from smoking if they choose to follow the warnings. People are smart enough to know that smoking is bad, and I don't think packaging has any influence over people's choices to smoke or not to smoke.
If cigarettes are permitted to be sold in plain packaging, this would create a scenario in which there would be no health hazard or "surgeon general" warnings on the packaging. While the dangers associated with cigarettes are not new news, it is still important that anyone that picks up a pack of cigarettes is openly reminded about the risk they are taking by smoking.