Distributed Shared Memory can be seen as a Service.
Server allows many users - in the Internet, or not only - to access the data in the Safe, Concurrent way.
Distributed Shared Memory is an Abstraction of Data Sharing Service for Computer Systems with separate Physical Memory.
Distributed Hash Tables (DHTs), used for example in the Torrent peer-to-peer file sharing systems, are examples of concrete implementations of the DSM Abstraction.
Concurrency is done per memory block, addressed properly.
Data can be replicated for speed of access & loss prevention.
Events System can be used for replicating data. Once a memory block within a group of such has it's data changed, including removal of data - which is also seen as a change, all memory blocks in a group can be notified and data can propagate properly, using properly Election Algorithm(-s) for selecting Process Coordinator if neccessary. This includes proper Processes Synchronization & Transactions - as in databases, financial Transactions are optional. Distributed Transactions have their uses here as well, they are using the Idea of Two-Phase Commits.
See also: , , , perhaps also , perhaps also  & , perhaps also , perhaps more.