Thanks for the good question. This semester, I am teaching at least partly from pdf slides and I post them when I make them, even if that is before lecture. I guess I am willing to wait and see if there are any bad effects before I try restricting access in any way. I would suggest that you try to get your administration to leave you alone. You may even strengthen your case by volunteering to collect data (exit surveys or whatnot) and letting the admins know what effect having the podcasts out has. It seems possible that attendence will go up--depending on how exciting the podcasts are. I wonder if there are other prof readers of slashdot with similar experience. Best Regards, tjh