Many home invaders actualy yell police. In fact it often goes unreported. If you look closely though in many events in small print someone often mentions they said something along the lines of "police" "sherriff's department" or some federal agency to throw people off guard and get the upper hand.
Other times they say "come out where I can see you", "hands up" or "freeze", in fact I think a poster just recently mentioned having a guy wander into his home and say something along those lines, like "come out where I can see you".
Yet if the actual police say "police" that is often evidence that you should have reasonably known they were police and not opened fire or resisted
Most such raids are in order to sieze drugs before someone can destroy "evidence". I personaly think violating the sanctity of the home in such a violent way simply for the sake of material evidence of something non violent is exceeding proper authority, and I applaud states that do not allow it. There is no reason most people cannot be arrested leaving the home, going to work, going to the store etc. If they are not a murder suspect, or a violent felony crime suspect, a raid into someone's "castle" shouldn't be justified.
That alone would cut down on the number of raids, and as a side benefit cut down on raids on the wrong address, bogus informant (read usualy drug addict with something to gain) information, etc.
One of the main reasons I am against "The war on drugs" is because of such abuses done in the name of fighting drugs. Prior to "the war on terrorism", the "war on drugs" was the primary way of circumventing the rights of the citizens. The "war on drugs" was contraversal though, but the "war on terrorism" is for people's safety so less oppose the errosion of rights from that angle, even though both are used by government in the same way to get what they want, total authority and control with minimal safeguards to inconvenience them, and everyone and everything tracked and monitored as much as people will allow. This makes control easier and more can be controlled with less effort.
Once control is too easy though, they expand what they want to control and what they care about as history has shown.
With limited resources, they focus on violent criminals. With tons of resources and power, they care about what you own, how you walk, what you eat, what you say, what is in your home, what is in your car, pockets, what you teach your kids, how you transport what you own, etc.
Its why the UK is in such a mess, they can really pick on people when they have so many resources and limited checks and balances, and the population becomes sheeple because they are told how unsafe and in danger they are all the time and how they only draw each and every breathe because thier wonderful government is out foiling plots, saving the day and keeping them safe. They come to believe this exageration and do not challenge abuses of power. After a few generations of this, its all they know and rely on it.
I personaly would rather see some drug problems in areas, the occasional terrorist attack, and not see America lose the essence of what has always made it unique and special: Liberty, Freedom.
How many died in 9/11? How many died in countless wars and struggles to protect the American way? An awful lot more than ever died in any terrorist attack, or all of them combined. In fact many many times more.
Here is an interesting piece on the American war for Independence:
http://www.detnews.com/apps/pbcs.dll/article?AID=/20070704/OPINION03/707040337/1036/ENT04
1 IN 4 SOLDIERS DIED, higher than in any war since. Only 1 in 40 died in WW2. It most certainly is not the peaceful marching through town, and occasional volley of gunfire as described for the benefit of children's minds.
They just did not have journalists and cameras everywhere to make people all share the emotions of every single event that happened.
Yet we throw it all away to battle some drugs, and to attempt to prevent the rare terrorist event.
So YES I would love to see some accountability for someone raiding the wrong home. I also think anyone firing at anyone (in the off chance that the home owner lives) breaking into thier home armed, if the resident is not a wanted fugitive should be immune to charges. How is a law abiding person supposed to know the difference between a criminal and an officer yelling "police" before barging in thier homes with guns.
These police look no different than a soldier now, especialy in low light. With gear anyone could purchase at the local military surplus store criminals can look like SWAT. When seconds count and tactical advantage could soon be lost, a person should not be worried if its a no knock wrong address, or organized criminals (many of whom have prior military experience and can and do raid in just as organized of fashion).