I was playing around with a 8.10 Ubuntu install and I must have pressed a key combination, because the screen magnification was turned on. It was all nice and smooth, the only problem was that I didn't want it! (BTW, almost the first thing I turn off after a fresh WinXP install is the accessibility shortcuts).
To turn it off, you can use compizconfig-settings-manager (found it via the Ubuntu forums). Install this package (if you are in an semi-offline situation, you need one additional dependency that is not installed by default - python-compizconfig), then go to System -> Preferences -> CompizConfig Settings Manager, click on Accesibility and uncheck "Enhanced Zoom Desktop". Warning! This setting gets reactivated every time you change the level of desktop effects (from Normal to Extra or the other way around), so you need to uncheck it again.