Large numbers of nodes making demands on the same server simultaneously can slow down everyone's experience. However, this can be mitigated by installing large amounts of RAM on the server (which speeds up read operations by improving caching performance), by adding more servers (which distributes the I/O workload), or by adding more disks to a RAID array (which distributes the "physical" I/O workload). In any case this is also a problem which can affect "any" client-server network to some extent, since, of course, fat clients also use servers to store user data.