An online video that when released attracts so much traffic that it crashes your site, the same way a blockbuster movie sells out theaters.
"Dr. Horrible should prove to be a profitable venture in the end, and will probably establish itself as the 'sitebuster' hit of the summer..." – Tubefilter
Pertaining to graffiti, when a toy hits a wall that has already been burned by an established writer, to make it look like they know each other, in an attempt to gain some credibility
In pro wrestling, a spinebuster is a move that involves a wrestlerpicking up his opponent, spinning, then finally slamming them down onto their back, or spine.