"Photoshop" is not a verb (and should be replaced with the equally-easy-to-say verb "enhance using Adobe® Photoshop® software") [1], but that doesn't stop people from using it as such anyway. The presence of an extra 's' doesn't impair meaning and focusing on it tends to be a distraction.
[1] http://www.adobe.com/legal/permissions/trademarks.html#photo...