The conflict arises in whether or not to describe the piece or present the audience with context for each piece. It is my stance that no, you should not. If there is a narrative, the piece should clearly represent that narrative. If not, then the audience should be free to take from the piece exactly what they find while viewing it. By explaining what the choreographer sees/feels/intends, you rob the audience of the chance to experience the work for themselves. This then turns the experience into a comparison between what they are seeing and what they have read.
My opinion differs (only slightly) in the performance of historically important repertoire. In this case, I think it is important to include information regarding why the piece is historic, the climate surrounding its creation, and why it is being performed now. Note that I did not say the piece itself should be explained, only facts about the piece. The same logic can be applied to pieces rooted in historic fact, but again only minor contextual fact and not interpretation should be provided.
The second form of this debate comes from collaboration. The scenario generally consists of a choreographer working with a musician, composer, set designer, actor, or another artistically inclined individual. Many of these individuals come from arts which focus on conveying a specific point to the observer. It may seem that if the audience does not 'get' exactly what was intended in the creation of the work, then the work has been a failure. This is not the mindset in most modern dance. There is room for interpretation and personal experience. In the event that the collaborator is invited to work with the choreographer, then the choreographer has the final say in just what goes into the program. It is an important discussion to have, but I again encourage the less-is-more technique.
On the other end is when a choreographer has been invited to work with another artist. And this is my other exception. Particularly when you (the choreographer) have been asked to create a work for an audience population that is unfamiliar with modern dance, it is prudent to include some form of program note.
Example: I was once asked to choreograph a piece for an organ concert. Beautiful music, in a beautiful hall, with a brilliant musician and fantastic dancers. Keep in mind however that the audience would be attending an organ concert, with some dance, and many have a history in viewing music performance. Some had never seen modern dance. The musician asked for programs notes and I sat and considered for a while just what to do. The route I chose was to explain the process the piece went through and the inspirations which guided my thoughts. This gave those unfamiliar with modern dance a context in which to view the piece but did not drive them to a tunnel visioned idea of what I thought about the piece. At least I hope that was the outcome.As usual, I would like to hear other thoughts on this topic. One should remember that the most important message of this topic, is that you should take into account every piece of information the audience receives as though it were choreography in the piece and form your decision on the total experience you would like your audience to encounter.