As you understand application virtualization sequences and streams the binary code to the endpoint client so that an application like MS Word or MS Access 2010 or MS Access 2007 can be run on the endpoint client. So in the case of an application like MS Office it will stream somewhere around 300MB – 1.5GB of data to each endpoint client. For application virtualization you can use products such as Microsoft App-V or Citrix XenApp or Novell Zenworks Application Virtualization. For Desktop virtualization you are most likely referring to presentation virtualization such as Microsoft Terminal Services or Citrix XenApp. Where they use protocols such as RDP or ICA which can be compressed and sends changes of the bitmap of the screen so that you are running the MS Office or Sharepoint in a centralized data center and they are performing all the computing on your server and the endpoint client is a display only device. This will require far less bandwidth and can reasonably run applications that are not graphics intensive such as streaming media, etc. in 100-500KB/sec bandwidth.
My personal experience says that if you have latencies beyond 150 to 200 kbps/s in Terminal Services, your users will start to call you/helpdesk.
As an example, if you run a POS windows application which is accessed via WAN with more than 150 kbps/s latency, you will start to wait for screen refreshes even with only 8 bit color depth.