A list of delusions taken from the psychiatric literature that don’t seem that delusional when you think about them:
“The earth is doomed”
– Patient with Alzheimer’s reported by Sultzer et al. (2003)“Bill Gates is destroying my files and spying on me”
– 32 year old patient reported by Podoll et al. (2000)“A local gang is going to mug me”
– South London patient reported by Freeman et al. (2001)“I drove two people mad when I was 11 to 14 years old”
– Patient from a study by Rhodes and Jakes (2000)“My thoughts are being controlled by TV newscasters”
– Inpatient reported by Noffsinger and Saleh (2000)
To quote Salvidor Dali “The only difference between me and a madman is that I’m not mad”.
Mind Hacks 
Brilliant.
There aren’t, after all, many beliefs that don’t fit someone’s definition of delusional.