During the dotcom boom, service providers were laying down cable at an incredible rate. But once the bubble burst, over 60 internet companies went bankrupt, and millions of miles of fiber infrastructure went dark. Other companies purchased these lines, but continued to build new cable lines, rather than reusing existing infrastructure (dark fiber). No one really knows how many miles of dark fiber networks there are, but some people believe it could significantly improve speeds for many internet users if these lines were operational. The problem is it’s expensive to do the work to make these networks functional, and not all dark fiber is practical for residential use.