Science is an inherently collaborative enterprise and this trend has accelerated over the past few decades. In particular, the Internet creates new possibilities for the organization of joint scientific work, specifically among geographically separated collaborators. A notable instance of Internet-mediated science is the collaboratory, or a laboratory without walls, where scientists are connected to each other, to instruments, and to data independent of time and location. This paper explores past and current collaboratory efforts to identify both characteristics that define a collaboratory and factors of collaboratory use that predict scientific success and failure. The paper concludes with an assessment of directions for future collaboratory development.