No they aren't! I have a friend that always says that. He's switching to gold ring hunting only because his theory is gold is being replaced but old coins aren't still being dropped. Always laugh when he says that. While he sits around and complains that all the spots are hunted out me and my other friend have been tearing up the old coins all last summer and fall.
There are ENDLESS places to hunt that have never seen a coil. The key is imagination. You must always be looking for places. While shopping drive around the back of the store. You might find an old lot or a small body of woods there that has seen activity. Hunting the woods along rivers and creeks is always good, as is ANY body of woods for that matter. You simply don't know what might have been there at one time. Hunting camps, old cabins, some guy bonking his girlfriend, and so on.
I keep a very keen eye out for any indications of activity when scouting woods. Old dates on trees. Depressions in the ground. Non-native trees (I *LOVE* looking for apple trees when they are in bloom. They stand out like a sore thumb). Pottery or glass shards, old stones piled in one place. Trees that are younger than the surrounding forest. Highways that trapped homesteads between them and a cliff, river, ridge, or private property with no way out so they were abandoned.
But it isn't just woods. Look for playgrounds in old neighborhoods. Chances are these tiny lot parks are built on where a house used to be. Train tressels often had construction camps near them. The tree lawn around stores or other places where nobody is likely to kick you out. There are endless places and possibilities but a negative attitude will not find them for you. Every time my friend starts getting down on old coin hunting I call my other buddy up and we go out and prove him wrong. I'd say this past summer was one of the best years I've ever had for old coins, and as I fine tune my "research" or scouting techniques I expect this year to be even better.
Heck, I even found a small lot behind a Mcdonalds parking lot in an old neighborhood. I know it was somebody's yard at one time because it's got a few shade trees and I can see the rope marks on a limb where a swing used to be. Can't wait to hunt that one either. Sometimes I'll read old "vanity" books that locals wrote. You'll find a lot of good leads in them as well. In fact, I just tracked down a spot where conterfitters were making coins on a high spot in a swamp from one of those old books. Guess where I'll be hunting this summer?
What I also try to do is take different streets when I go to the store or something so I can look for new places. Even if I'm just leaving my house I'll take the next street over to get somewhere. Found out a patch of land near some railroad tracks was scraped last summer by doing that. Some locals had cleaned this spot out several years ago and got some good coins. I never got anything and the ground was very mineralized. When I saw that they had scraped about 14" of dirt off the lot I called my friend and we were there that night. Then I started popping the coins that were either too deep or masked before the the layer they stripped off. Up until they had removed that topsoil I had hit this spot four or five times only because I knew what had came out of there before but never got anything. This was prior to me owning a GT which might have produced there. Point being watch for construction sites as well.
One other thing about hunting woods: Keep in mind that as trees get older the underbrush and briars go away. For that reason alone you are probably the first person to swing a coil even in a small wooded lot right in the middle of a city. I watch for tree growth that looks to be just old enough to start killing the briars and brush under them. Those are for sure virgin areas even if they are right next to an old school because it was too thick to hunt just a few years ago.