My mom says the strips pull the edge out of whack. Being a professional, she keeps her finest in a knife roll, and her "everyday" (which are pretty darn nice) in a wooden rack fashioned by my grandfather and screwed to the side of the wooden butcher block. I don't have that kind of space. We have a strip.
So I put the question to Margery, our resident knife expert. Here's what she said:
I too used to tell customers that I didn't trust magnetic strips because I felt that they could possibly cause misalignment on a molecular level. I brought up this conversation with a mechanical engineer and he assured me that that was impossible.
I keep my knives on a magnetic strip in my kitchen (because we don't have very much drawer or counter space). I can't really say it causes my knives to get dull faster because I sharpen them regularly. Though, if the knife is placed on the magnetic strip lazily, with the edge touching first, that is bad for the knife. Also, wooden blocks that have perpendicular slats can be bad for knives because the knife slides against the wood every time you put it in or pull it out of the block. Horizontal is best.
(You can find Margery sharpening knives outside Bowery Kitchen Supply in the Chelsea Market Building at 460 West 16 Street between 9th and 10th Avenues, Saturday and Wednesdays from 12 noon - 6 P.M.)