The $72 trillion was real math. US copyright law allows up to $150,000 per willful infringement, and the RIAA argued that meant $150,000 per download, per song, for 11,000 songs across 50 million LimeWire users. Multiply it out and you get more money than exists on Earth. Judge Kimba Wood ran the numbers in her 2011 ruling and wrote that the award would exceed everything the recording industry had earned since Edison invented the phonograph in 1877. Global wealth at the time was estimated…