Dust jacket on or off when reading?

I'm wondering what my book loving friends do when they read a hardcover book. Do you read it with the dust jacket on, or do you take the dust jacket off before you read it?

I personally always take the dust jacket off first, otherwise it slips on the book while I am reading. I am always afraid that I am going to wrinkle the dust jacket when that happens, not to mention that it can be very distracting sliding on the book while you are reading!

I usually take the dust jackets off when reading so they stay nice and don't become ripped or creased.