Key distribution is a problem, yes (as discussed in other comments here). Upload bandwidth isn't so much of a problem with the number of participants, as you o

Key distribution is a problem, yes (as discussed in other comments here). Upload bandwidth isn't so much of a problem with the number of participants, as you of course wouldn't encrypt the whole data stream separately for each peer. Instead, you would encrypt it with a rotating symmetrical key that you can then safely exchange with all peers (at negligible bandwidth cost). You would still depend on the server to replicate your encrypted stream (and do NAT traversal etc), but it wouldn't be able to peek inside. A separate problem is that you usually want your server to actually create reencoded video of your stream for participants with bad internet. There's potentially some ways to do that without server involvement with some clever video encoding (so that instead of reencoding you can just throw away some chunks), but afaik there's nothing production ready for video codecs here.