Zeiss Lens Cleaner

Apple states: +Don’t use window cleaners, household cleaners, aerosol sprays, solvents, alcohol, ammonia, or abrasives to clean iPhone. If your iPhone has an oleophobic coating on the screen (iPhone 3GS only), simply wipe your iPhone’s screen with a soft, lint-free cloth to remove oil left by your hands and face.+

Zeiss Lens Cleaner is (nearly) pure isopropyl alcohol. So yes, it's possible you diminished the effectiveness of the oleophobic surface.

jddj wrote:
I have used a cloth slightly dampened with Zeiss Lens (eyeglass) Cleaner half a dozen times on my 3GS screen. Never a direct spray! Now I am concerned that the hydrophobic surface may have been damaged. I am strictly using a microfiber fine cloth now. Anyone have experience of this sort or information on the use of any lens cleaner (not Windex).

All you should use on the iPhone screen is a soft cloth to remove grease and finger prints and the cloth should not have any cleaning sprays etc on it.

With the 3GS having the hydrophobic coating, this makes the removal of grease and finger prints much easier than a non hydrophobic coated screen.