This is a topic near and dear to me, as I am a scientist and a writer/public speaker.
I think that everyone, including scientists, should have as much knowledge outside their field as they can. People that only know one thing become tedious very quickly. They also have no perspective.
I do not think every scientist should be forced to discuss their work with the public. I know quite a few scientists, and while the majority would be adequate to explain some scientific observation to a layman, there are some that should be bound, gagged and thrown into a dark room and never allowed to utter a word to a taxpayer. They would do more harm than good.
This is not an aspersion on scientists; I think the ratio of speakers to non-speakers would be the same for most professions (most; lawyers, TV personalities and the like would be the obvious exception). However, it might be a good idea that each project of a given group have a speaker involved that can explain what they are doing. The public deserves not only to know what scientists are doing but they should understand it as well. It takes a good speaker to do that…
… but it takes an educated public as well. It’s not necessarily scientists’ fault that the public is overrun with fuzzy thinking such as astrology, creationism and the like (no hijacking, please). We have to meet halfway. Scientists need to learn how to communicate more effectively, and the public needs to learn how to think critically and rationally. When these happen, things will improve.