The other big problem is that laptops are designed to be the smaller possible, and because of that they are often very badly cooled. Personnally, if I use my CPU at 100% (without using the GPU, and with no dust inside the laptop), it has to throttle a little bit, and the temperature is 99°C. That's way too much if you want it to have a long life. So there are two solution : you find ways to cool the laptop better, or you use less the CPU (there are parameters for that, usually).
So I agree with the others, mining with a laptop is not a good deal. Even more for Ethereum that will certainly not pump a lot.
However, if you want to mine just for fun (like me
), then why not. But I would personnally recommend to mine new coins that are not very known and you really strongly believe in. If you can't afford buying a few ones, this can be another way to get them (against some electricity). 