"Obviously this ban [on camera phones in election booths] doesn't actually prevent voters from selling their votes - votes were being bought and sold long before cameras were invented - but the lack of photographic evidence reduces the economic efficiency of the transaction."
In some societies, nearly everybody has a mobile phone, and nearly every phone can take crude photographs. And while people often leave proper cameras at home, except on special occasions, most people carry a mobile at all time. This has led to a heightened expectation of photographic evidence - including evidence of wrong-doing. For example, gang members recording antisocial behaviour (such as "happy-slapping" - a physically violent form of bullying framed as slapstick) to boost their social standing within the gang.
The same technology can of course be used for more praiseworthy purposes: for example, to record interviews and video diaries from areas where traditional journalism is constrained and independent journalists are banned. The smuggled pictures and video perform the function of samizdat.
As it happens, both happy-slapping and samizdat are subversive, although in very different ways. But the justice system also relies on photographic evidence: older readers may remember the "twenty seven eight-by-ten colour glossy pictures with circles and arrows and a paragraph on the back of each one" taken by Officer Obie in evidence against one Arlo Guthrie for littering on Thanksgiving [source: Alice's Restaurant (lyrics) (track)]. And then of course there are surveillance cameras ...
But this widespread expectation of photographic evidence devalues oral testimony. We don't trust words as much these days: if there aren't any pictures, it probably isn't true. In the past, even bribery and corruption relied on trust, because there wasn't any alternative; the camera (or rather the way society increasingly uses cameras) undermines trust.