Indeed: Ahmadinejad's supporters have released photoshopped images showing that the rallies supporting the regime are bigger than they are in reality. Trick photography was used for a similar affect by the US in Baghdad.
However, it will remain difficult to have multiple corroborating photographs of the same event that all match up. Making the truth match up is easy, but making forged videos and photos consistent when lots of separate people are releasing them is hard because it's hard to keep lies of any kind consistent without the liars being in cahoots.
Which means that reports from random people are probably more reliable than journalists or governments. Governments and news organizations can collaborate on a lie better than mobs.
However, it will remain difficult to have multiple corroborating photographs of the same event that all match up. Making the truth match up is easy, but making forged videos and photos consistent when lots of separate people are releasing them is hard because it's hard to keep lies of any kind consistent without the liars being in cahoots.
Which means that reports from random people are probably more reliable than journalists or governments. Governments and news organizations can collaborate on a lie better than mobs.