You can yell "Fire" in a crowded theater and get an immediate reaction. But if you yell "Fire" at a bonfire,... you'll get strange looks.
Some things are grotesquly obvious and need no attention brought to them. While using the right comment at a place where it will be HEARD is often a subtle masterpiece.
This being said, there is no single place that works for all comments. If your product oir service fits the masses, great! but typically you will have a core audience. Each message must be tailored to the intended audience. The audience can be difined by age, sex, income or even geographic information. It is best to find the largest (similar) audience in the same "setting" to achieve the best results.
Now you have to find persons "in the market" for your product (that's a whole other blog!) and talk with them about their needs. Step back, evaluate your message, and determine if you are yelling "Fire" at a fire, or if you will cause a stampede of customers to your business! Putting this all together correctly is the secret!
Saying the right thing, at the right time, to the right person, in the right place, makes for a successfull transaction of information!