This article is about three trends in computer hardware, and some of the challenges and opportunities that I think they provide for the distributed computing community. A common theme in all of these trends is that hardware is moving away from assumptions that have often been made about the relative performance of different operations (e.g., computation versus network communication), the reliability of operations (e.g., that memory accesses are reliable, but network communication is not), and

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... en some of the basic properties of the system (e.g., that the contents of main memory are lost on power failure). Section 1 introduces "rack-scale" systems and the kinds of properties likely in their interconnect networks. Section 2 describes challenges in systems with shared physical memory but without hardware cache coherence. Section 3 discusses nonvolatile byte-addressable memory. The article is based in part on my talk at the ACM PODC 2014 event in celebration of Maurice Herlihy's sixtieth birthday.