Originally posted by Blair Wind

People need to make clear distinctions about things:
When blown up in HUMAN form, it hurts him to recreate himself. This has happened on panel with Northstar
When blown up/evaporated or "transmuted" into water/mist in ICE form (Sentinels, teleported into a wall, exploding arrow, some vampire/pyro guy) he can reconstruct himself easily. No pain involved.
Teleportation and what Bobby does are similar things but not exact. The thing that you must remember here is that in the Marvel universe teleporters (most notably Nightcrawler who goes against Magneto most out of all the teleporters I know) travel along magnetic lines. THAT is why teleportation does not go through, because he does not allow it. What Bobby does is not related to magnetic lines in the least, therefore has nothing to do with the picture.
Bobby does not direct a "line" of cold. Say he wanted to freeze a can of soda fifty feet away. He does not need to lower the temperature in the fifty feet between him and the soda. He can lower the temperature of the soda in and of itself. Therefore, any magnetic "walls" would really be....nothing. It would be as if it did not exist. Lowering Magneto's very own molecules so he becomes a living statue ftw.
Because ice does not exist in space....?
Look, the thing is, Iceman can exist as water vapor, and as good as Magneto is, he would not be able to tell what water vapor was "Iceman water vapor" and what water vapor was just water vapor. Any and all physical attacks would prove useless as he can exist as water vapor, water, or reconstruct himself rather easily once in Ice form.
I'll admit, any physical attacks on Magneto would prove useless. However, any direct slowing of Magneto's molecules, or existing inside of him and then literally exploding from inside of him (as he has done to someone before) or any other method of attack and he would win.