The first in the "good deeds" series of television commercial for Liberty Mutual produced by advertising agency Hill Holliday. It features strangers doing good deeds for strangers, which inspires onlookers to do the same.
The song is "Half Acre," by Hem. It's on their 2002 album "Rabbit Songs." More information about the band can be found at their MySpace page here: http://www.myspace.com/hem