way to keep subwoofers from blowing?

Why don't amps have some way of monitoring and self-adjusting gains? This would nearly eliminate clipping, right? I know that this way it would always be 'wide-open' but it seems someone would have tried by now.

I guess it wouldn't be worth it, though. Cost of parts, new designing, production, no to mention loss of repairs due to proper gain settings...

Yes, it would be very expensive to add a circuit like that.  I believe Bang and Olafsun have something similar for their high-end self-powered home stereo speakers.

Well, for starters I disagree that you couldn't stop people from blowing their woofers with a fuse. Lets say a coil can handle 500 watts with no woofer movement using dc current. 500 watts is below the level of power it takes for the speaker to reach the limits of it's excursion. If you set that baby to trip at a low enough level it's not going to fry before it trips. I'm sure some people would try to bypass this to get the max out of their woofer though. You could also use something in amplifiers that once it reached x watts it will shut off. This would not be too expensive to produce. I'm sure we could come up with something simple and cheap using a zener diode and a few other spare parts. This sounds like a fun project. Instead of just coming here saying "oh that wouldn't work" with no proof why not prove me wrong and test it out? First try say a .5 amp fuse on a subwoofer and see if you can blow it. I don't think that is possible, but I could be wrong. Although I seriously doubt that any company would make amps and subwoofer you couldn't destroy it's worth a try to get them to do so. I think people would love the sense of security and it would also give companies more incentive to improve their products.

We apply a sticker over the amp settings, they are virtually impossible to re-apply after removed. It is amazing how many people try to re-stick them after "turning up the power"  .

I was just trying to make a point when I said use a .5 amp fuse. You hae a point about the over excursion in poor or no enclosure. Now you have me wondering how many watts it takes with no enclosure to throw the cone (destroy the surround) without an enclosure compared to with a proper inenclosure. And couldn't you use bump plates to keep the woofer from destroying the surround? I used to have an 18" sub that had a bump plate on it. When it hit that bump plate it made a loud clapping noise. None of my newer subwoofers have had them. Do they still use them?  So what do you think about a fused sub with a bump plate? In a way it seems silly to have to put in safe guards to guard people from themselves, but that's why we make seat belt laws, a microwave automatically stops transmitting when you open the door, there are fences around electrical stations, etc. Imagine what would happen if one day god took out all safety precautions out of everything. Just something to ponder...