2. Traditional thin client solutions are not desktop virtualizationBy far the most popular form of server-based, thin client computing relies on Microsoft Terminal Services (recently renamed Remote Desktop Services), which lets multiple users share the same instance of Windows. Terminal Services is often paired with Citrix XenApp (formerly known as Presentation Server and, before that, MetaFrame), which adds management features and improves performance -- no hypervisors or VMs here. The main drawbacks: Some applications run poorly or not at all in this shared environment, and individuals can't customize their user experience the way they can with virtual machines or real desktops. Nonetheless, people often refer to traditional thin client solutions as desktop virtualization because the basic goal is the same: to consolidate desktop computing at the server.
3. Desktop virtualization and VDI mean pretty much the same thingVMware was first to promote the VDI (virtual desktop infrastructure) terminology, but Microsoft and Citrix have followed suit, offering VDI solutions of their own based on the Hyper-V and XenServer hypervisors, respectively. Think of it this way: VDI refers to the basic architecture for desktop virtualization, where a VM for each user runs on the server.
4. Don't confuse desktop virtualization with ... desktop virtualizationThe desktop virtualization we're talking about refers to server-based computing. But "desktop virtualization" also refers to running virtual machines on desktop systems, using such desktop virtualization solutions as Microsoft Virtual PC, VMware Fusion, or Parallels Desktop. Probably the most common use of this sort of desktop virtualization is running Windows in a Parallels or Fusion VM on the Mac. In other words, this has nothing to do with server-based computing.
5. No server-based computing solution supports the same range of hardware as a desktopThe Windows folks in Redmond spend half their lives ensuring compatibility with every printer, graphics card, sound card, scanner, and quirky USB device. With thin clients, your support for hardware is going to be pretty generic, and some items won't work at all. Other limitations are introduced by the fact that users interact with their VMs over the network. Multimedia, videos, and Flash apps can be problematic.