I have a 125g freshwater with a dual 1,200gph HOB overflow set up for 2 years. I've lost power quite a few times but have never, never, had a problem with it. I've heard these "warnings" before but have not met anyone that has them set up properly have a problem with them. I say properly loosely because like anything in the hobby, if it's not set up properly you can have issues. Like when a friend of mine did not heed my warnings about sticking his return pipes so low in his 220g. He covered the hole I drilled in the retrun with putty because where he stuck it in the water it would sometimes gulp a bubble. Well one day he came home to 80g of water in his kitchen. So I don't care if your tank is drilled or HOB. They each must be set up correctly. That is the key, not blaming the box itself. Just like the next important piece of advice. Just stuffing a 10g under a 55 might not be a good idea. In the event of a power failure you could end up accidenlty overfilling it. Let's say you buy a nice skimmer and stuff it in the 10g. You run it with low water levels for a few weeks. Someone tells you 8" of water depth makes it work better. So you adjust the return pump aand add more water to the tank. Sure enough it works great. So you are now happy that your skimmer works better but forgot that you seriously limit the amount of back siphon water your sump can hold in a power failure.

So again we must take responsibility and make sure our equipment is functioning correctly and we have as many fail safes as possible.