Your ear feels warm because you had the phone pressed against it so the ear was not cooled by air. Same thing occurs with a land-line telephone hand-set, but to a lesser degree because the handset doesn't generate heat, especially compared to things like iPhones that have high powered computers built in. Cell phones are smaller, so the hand is held closer to the ear and that adds heat (infrared radiation same as a nice fireplace).
Anecdotes like "feel like my ear has been microwaved" do not constitute evidence for "simply cannot be good for your head".
The tell-tale word here is "simply".
For something where there is not an obvious clear unambiguous mechanism like smoke to disease, then you need some very careful science and statistical study to find a disease effect, if there is any at all. With smoke the question was never whether smoke is bad for you because people died of smoke inhalation in fires for millenia. The question was whether tobacco smoke was safe enough. A very little investigation made it clear that it was not safe enough, but of course the history is that the tobacco companies dragged it out with corrupt and illegal tactics and practices, doing everything they could to sabotage the science.
There may be a very low level disease effect from excessive cell phone use. There is not sufficient scientific evidence to establish that at this time, let alone putting warnings on the product.
To some extent, people need to be a little less fearful and just get on with life. There are no guarantees about life. Too much fear about this or that leads to paralysis. There is a risk to staying in bed and a risk to getting out of bed.
I bet that the positive health effects of cell phone use (friendship, better income) are much more powerful than any possible disease effect from the non-ionizing radiation.
It is best to keep a balanced perspective on risks. People are way too fearful of dieing from flying but drive like idiots to and from the airport where the risk of dieing is much greater even if they drive perfectly. I wonder if all the people fearful of a disease effect from their cell phone are perfect at diet, exercise, and maintaining mental agility through life long learning.
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