Had a good chuckle at this:
http://www.theregister.co.uk/2009/05/07/microsoft_search_built_on_open_source/

Summary:
Seems that redmond aquired hotmail in '97; built on BSD!
Despite their best efforts to rip out the guts & replace it with their own flavour, rusults remain a largely mixed bag.

Now with the "great new search engine", Kumo, they where compelled to yet again leverage FOSS technologies, Hadoop, to get a function system working.

Irony so thick, I can taste it ... :D