Brandnames turning into verbs is nothing new. Google turned 'verb' a while back officially, and can be found in several dictionaries all over the world. You could think that the brand owner would like it this when a product (or brand) becomes a commodity. Well, not every brand.....
Adobe has a section on the 'Photoshop' usage on their website [mirror]. It seems that photoshopping is a bad verb. Why? I don't know. No matter how good or bad an image or photo is altered or with what tool. The most common remark is 'PHOTOSHOPPED'. All this means is that people associate image manipulation with Adobe Photoshop. There's a reason that this piece of software is on top of the image manipulation food chain. It's simply the best (and probably the most expensive by the way :) ).
After looking for 'google' in the Apple OS X Dictionary, I also tried 'photoshop'. and guess what I found:
/me sits back and wonders when Apple (or even me) receives a letter from an Adobe attorney :) for the incorrect usage of the Photoshop brand.