As far as addiction, there is chemical addiction, and psychological addition. The former isn't present for a lot of drugs. The latter is very hard to control for, because it really depends on the individual. People can definitely find comfort in escape from reality that psychedelics offer, which can lead to dependence.
However, given an addictive personality, psilocybin use is still safer than comparable drugs, including weed. First, the method of intake through digestive tract is generally better for health than smoking. Secondly, there are no negative withdrawal symptoms from stopping, even with micro-dosing (so in the case of your festival goers, the supposed straight week of use produces no negative withdrawal effects). Thirdly, the desire to get a stronger escape from reality will involve someone taking a higher dose, which isn't a euphoric experience like weed or MDMA can produce - its fairly exhausting even when you are having a good time.
So in the end, given the society view to alcohol and its comparable effects, psilocybin should absolutely be decriminalized and promoted as medicine for use, especially with therapy.