Twitter tends to represent an unfounded resurgence of methodological realism, yet the medium is not merely a conduit for messages that reflect the true sentiment of all actors involved. Rather it is a structuring device for communication based on the idea of a "network" a priori. It is also a business. In this article, I discuss the technical and practical issues that simultaneously make Twitter feel like a profound window to the social world while masking many absences and inequalities. I critique the absence of lurkers, the focus on streaming data and the emphasis on personalization. Greater care must be made to triangulate Twitter data with traditional social science theories and methods.