The USSR renamed its rocket base Baikonur in 1961 to keep the Soviet space program a secret. Residents of the original Baikonur, hundreds of km away, took advantage of the resulting confusion by ordering many valuable supplies for themselves before the scam was discovered.
Someone tricked a Nigerian scammer into hand writing an entire Harry Potter novel, the whole 293 pages and scanned with a scan width of 1200 pixel. He offered to pay him $100 per page if he was willing to do the work.
Nigerian 419 scammers convinced Banco Noroeste executives to deposit $242 million in their Cayman bank accounts.