In this digital age, the adage "a picture never lies" is about as accurate as saying "a politician never lies". I am used to receiving many pictures forwarded back and forth through the internet by friends. Being a user of photoshop to modify images, I can tell if there is a strong likelihood that an image has been digitally modified. Perhaps the adage should now read "If a picture looks too fantastic to be true, it probably isn't true."
Video clips tend to have more credibility but even then one should not believe everything he sees unless it is "live". Yes, even video clips can be digitally modified, as in the case of a sawn off body of a horse running across the paddock. Or that of a sawn off woman in the park who uses her hands to "walk" away from her legs.
Fortunately, in the internet the amount of true and accurate information far outweighs mis-information or lies. The danger is that sometimes you will get lies masquerading as truths. One just cannot be too careful. Perhaps we should allocate one day in the year to spread April Fool jokes around the internet just to remind people not to believe everything he reads and sees, or receives in the email.