"Flipped Classroom" is a relatively new idea, where the teacher works with students on projects and what would be typically homework instead of a lecture and the students get the "lecture" at home, usually through a video (like from Kahn Academy). The proponents of this model say that it offers the teacher more time to work with students on projects and applying the knowledge, rather than spending time delivering that knowledge.
I have some issues with the "Flipped Classroom" model. The first is that this model leads to a lot of homework for students if they have to watch videos of lectures. This is not only asking a lot of the students to be able to do, but not anything really new or inventive. Students have other obligations and time commitments and watching video lectures is time consuming.
Students may not have access to a computer at home with high speed internet (needed to watch these videos). Many of my students do not have a computer at home, or have a dial up network. Many do not have anywhere quiet to work or listen to these video lectures.
While watching a video lecture, a student has no one to ask questions of. They would have to write down the question and then ask their teacher the next day. This may cause students to get confused early on and just shut off the video. It is very passive - there is no interaction and no discussion with others. This not how we want our students to learn.
I do share video sites with my students so that they can use them as a review or reference (or even different delivery style and explanation). But, it's not required of them. There are some great online videos available for students to use to learn material, but I don't think it should be the primary delivery method for them.
I use "lecture" of a sort in my Physics class. I use PowerPoint, Prezi, animations, demonstrations, and discussions to present material, ideas, content, and such with my students. They can ask questions of me. We can discuss the topic and it's applications. I also show them short videos in class and pause it at different points to answer questions or discuss what's going on with them. The "lectures" are short and give the basic information for a topic. The students then explore the topics in more depth using projects, labs, and virtual investigations and simulations. They get packets for each topic with a summary of the topic and problems (these packets are much better than the textbook). They start these problems in class and then finish them for homework. We go over the problems in class after they complete them. I have a class website and blogs for each class with links and other resources. For students that don't have computer access at home, I share different printed resources with them.
In my AP Physics class, I have to modify things a little. I present the content for each topic via a PowerPoint presentation and we discuss the topics. The students also have a textbook to read, problems to do, and they do projects and labs. These students typically have much more access to computers at home and are more independent learners. I cover the main points in class and they explore the rest on their own. There are some great online lecture videos for AP Physics that they can use for review or reinforcement, but again, they are not required.
The "Flipped Classroom" may work in some schools and with some students, but it is not a good fit for many students and should be used cautiously.