There are many potential detriments to consider in regards to podcasting. I have no way of knowing that students actually listen to the podcast; they could be missing instruction, and I have no way of knowing that. Also, the availability of listening whenever they want eliminates the need to come to class, causing a loss of interaction. On the flip side, the availability to listen to a lecture that is missed could be a benefit if students are absent. Another benefit is the use of podcasts to communicate with parents or substitute teachers.
If a teacher uses a podcast, students are obligated to decide whether they want to attend class in a traditional way or if they would rather listen to the podcast later. Choosing to utilize podcasting puts more responsibility on students. I think students are also obligated to inform the teacher if there is a way to use a podcast to best promote their success. Is the podcast a really helpful study tool? Is it easier to take notes with because it can be paused? Questions like this are important for students to think about in order to help the teacher help them.
I do not think that in a high school (or lower) class attendance should be optional. I can see perhaps taking that into consideration for college students, but if attendance is optional in a high school class, problems will arise. I feel that implementing podcasts as an alternative to in-class lectures is very dangerous and should not be considered for primary or secondary education.
I think the best way for me to integrate a podcast into a classroom is to record lectures and only make them available to students when they are absent. When a students is absent from class, they are expected to make up work but still miss out on so much instruction; a recorded podcast can help with that problem. Also, pre-recording a lesson for a sub to play in class could be really beneficial. When I was in high school, a sub meant it was an easy day to do a generally meaningless task to fill the hour because the substitute may not have been or felt qualified to actually teach. By recording the lesson for my students, class time is not lost or wasted just because I cannot be present.