“Secondly, there is currently no back channel, or any way for your computer or other device to talk back to the television station to request a web page, upload photos, etc. That backchannel would have to be over some other system, either a dial-up telephone line or a wireless cell phone service of some sort.”
Yes, I was aware of the lack of back channel but wanted to deal first with the question of whether they could -send- unique/separate data to large numbers of people.
Ideas for sending back info in and of itself can make for interesting contemplation and sharing as a group.
There is already a method defined within the ATSC standard to multicast data. the problem again is the limited amount of data available. When the ATSC standard was developed 15 years ago the text data carousel was adequate. But today everyone wants to stream video, and that’s what TV stations do - four or five streams at a time.