The year was 1941 and in Nazi Germany, a movement was started. They called themselves the "Swing Kids" and they followed British fashion trends and listened to American Big Band music. This teens-to-mid-20s culture grew out of its disapproval of the social norms. From this point on in history, for every culture, there has been a sub-culture known commonly as "anti-culture." In the '60s it was the hippies, the '80s urban rap, the '90s grunge and the 2000s hipsters.
The modern hipster is very much different from the anti-cultures of previous decades. This is because they cannot be defined by any typical "hipster standard." A modern hipster may listen to any assortment of music, except for Top 40. This means that the term "hipster" is all-encompassing. The same follows for fashion trends. The point of being a hipster is to avoid pop culture at all costs.
This is very different to what a scenester encompasses. A scenester exists solely for one reason: they need to be seen at local shows. They follow their own trends within their subculture and are prone to imitation instead of imagination. A hipster will wear whatever feels comfortable and whatever they like. A scenester, on the other hand, will wear whatever their favourite artist wore at the last show.
These two subcultures do not coexist peacefully. Hipsters would socially destroy anyone who would think to call them a scenester. This is because scenesters are a group of socially awkward, immature and uncomfortable wanna-be cool kids. Although a hipster refuses to acknowledge the fact that he or she is actually a hipster, a true hipster will not care about the label. Hipsters avoid the use of this term because of the negative connotations associated with it. Because society misuses the terms so often, these terms are commonly used interchangeably. They are not interchangeable.
Hipsters are a valuable subculture redefining and stretching the boundaries of the social norm. Scenesters are a mindless cloning tool used by companies like American Apparel to increase quarterly sales figures.
The terms are only interchangeable to those who do not understand what they mean.