New EOS-M, a mistake!

That's just marketing. There is more engineering in a lens with stabilization so it definitely will cost more to manufacturer.
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Tymevest

Who cares how much it costs to manufacture? Does anybody really know anyway?

What matter for a consumer is how much you pay for the lens at the counter or checkout.

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I can see the light at the end of the tunnel...of my lens.

Then look at 70-200 F2.8 vs F2.8 IS mark I, or F4 vs F4 IS. good IS on large lenses definitely cost more.

What's more is that lens IS often adds more elements into the lens, which in turn reduces light transmission. I think this was the reason why the new 24-70 still doesnt have IS - to ensure maximum light transmission. If you look at DXO's lens tests, most IS enabled lens cut around extra 0.1 to 0.2 stops of light than non-IS comparable lens. 24-105 F4 in fact cuts out 1.1 stop of light, resulting an actual transmission of 5.1 stops.

Lastly in lens IS is one more thing to break (and it appears to break more often than the lens itself) and very costly to repair.

Having said that, there are two advantages with ILIS, first it seems to give more stablisation than IBIS, right now by about 1 to 2 stops, secondly and more importantly it makes image through OVF stablised.

In My view however, the first advantage is not so noticeable when it comes to wide angle lenses, because half the time your shutter speed are limited by subject's motion, and the other half the time, I dont think ILIS really gives your 4 stop stabilisation at 17mm, how often does anyone take a pictures handheld at 1s shutter speed? most people buying mirrorless will only use wide to short-tele lens anyway - who shoots 300mm with mirrorless? So overall this advantage is rather limited.

The second advantage is not so noticeable if you dot have an OVF, for a mirrorless camera, what you see is what the sensor sees, so if the sensor is stablised then surely EVF gives you a stablised image, and I am sure as of 2012 with digic 5 they could even make the processor to stablise the image before it comes onto the LCD.

So there, I would say it was a mistake to do ILIS with mirrorless...

To solve the viewfinder issue, I guess they could do something like this and make at least some people happy:

http://www.behance.net/gallery/SMAECK-Camera-concept/5604773