There are multiple artists with this name: 1) A popular British rock band. 2) A Belgian jazz band. 3) A Canadian punk band. 4) A British post-punk duo.
1) Placebo is a three-piece alternative rock band, formed in London, United Kingdom, when former Luxembourg schoolmates Brian Molko and Stefan Olsdal - who never actually spoke to each other at the time - met by accident at South Kensington train station in 1994. During their 'accidental' meet, Molko invited Olsdal to one of his gigs, where Olsdal was impressed by Molko's unique vocals.