The term 'sellout' has been around for a few generations. Often used as a negative term used to describe somebody that conforms to a particular way of doing something such a dress, vernacular, or type of
work.
Recently it has been used in the
indy music scene to a large extent since the explosion of
ska, punk,
hardcore, and indy
rock.
One earns the label of sellout by alienating their
core fans that have supported the band by changing their style to be more appealing to a broader audience, often become what they were rebeling against in the very beginning. While some may call this "evolution of the artist/music" one has to remember that evolution is a gradual change and not sudden and drastic, the losing of edge, and doesn't accompany a bigger record label.
While many bands out there refuse to be labeled as sellouts, they are often putting out records and being quoted as saying "This is more true to our
core sound, where we started".