nma did a succinct job of explaining what tone mapping is actually all about. I've always said that the objections many photographers have to "HDR" is not so much the HDR foundation per se, but that they don't like the way some photographers handle the tone mapping part of an HDR workflow, frequently too aggressively.
Alan is right that HDR images, no matter how photometrically correct, can still look unnatural. It's something I struggle with a lot. At first, I made every effort to go down the path of attempting a completely realistic look. I'd often get frustrated by how much work it took to coax a traditional looking image out of an HDR original.
Then I met Dan Burkholder, and learned to embrace the surreal grunge look. Not my instinctual style, but I came to appreciate it nonetheless. Now I can put an enormous amount of tone mapped weirdness into prints, and people just love them all the more for it. In fact, the more outrageous my prints are, the more likely I am to sell them. Go figure.
But, instinct being instinct, I still try for something more traditional when I think it's appropriate. Take a look at the attached images. The church image looks pretty standard, but in fact it's an HDR from a 5 stop span. I knew there was no way my camera had enough dynamic range to hold the details in the whiter than white statue under blaring New Mexico sun, while still capturing the shadowed wall with enough light to prevent noise. But when I started tone mapping the sequence, it looked very strange. I didn't put much time into that image, but I did play with the HDR until I got some detail back into the statue, but not too much. You can judge whether or not I was successful. You can see from the straight train image that the black and white result is tone mapped beyond any level of reality. Again, a 5 stop range, only with this one, I was going for complete fantasy.