This would be a good TiVo feature: a warning asking you to confirm a channel change if you're watching live TV on delay. TiVo allows you to pause as you watch TV (like when you need to go to the bathroom and you're watching a football game, say the AFC Championship Game). If you pause enough, you sometimes get "behind" the actual live game. Now it's not the same as having it recorded, because it's only temporary and there's a buffer max (you can't get more than 30 minutes behind the "live" action). Unfortunately, if you change channels (like when the cat climbs on your lap, so you try and move him off of it and onto the sofa, whereby you accidentally place him on the remote control, and his enormous paw happens to hit the channel "up" button on the remote) while watching not-live TV, you lose whatever's in this buffer and there's no way to recover it.
TiVo should give you a warning along the lines of, "Hey! You know you're not watching live TV here. You're behind. Do you really want to change the channel? Because you can't get back to this point if you do, and that means you'll *miss* the Steeler's field goal attempt, which I think you might be interested in seeing, only because New England is going to block it and run it back for a touchdown. If you change the channel now (perhaps by accident), and even if you come back really really fast, you'll just jump ahead seven minutes to the current action. Oh, you'll see the score is 21-3, but you won't know why. Now, tell me the truth: Do you really want to change the channel?" Yeah, I think that would be a good TiVo feature.