@whoever
@Julia Smith: Xserver and Mainframes? Tradditional IBM mainframes (running MVS, IMS, CMS, TSO etc) either never understood X, or were slow to adopt it (OpenMVS, which became z/OS, has/had a POSIX compatibility layer that added X Clients) but it is clearly nonsensical to have an X Server running on a Mainframe. IBM mainframe graphics either used channel attached workstations (often running AIX and proprietary channel-based communications) for high performance work, or 3278 graphics terminals for business type graphics.
Can't really talk about other vendors mainframe offerings, because I never had any real exposure to them.
@Mage : Understand what you are saying, but being a bit picky, I would like to point out that vt100's were not graphics capable terminals (unless you include the box-characters in the advanced video option). In the vt1XX line, you would be using a vt131 or vt132 for graphics, and the followups were the vt240 and vt241, (this last being a colour terminal!) The standard they used was a propriety ANSI-extension that was called ReGiS (capitalization may be wrong) that was proposed as a standard, but fell by the way-side.
Still, I would have thought that using a browser based rendering engine will never be really efficient unless it grows into a full blown fully functional 3D rendering device (like OpenGL or possibly DirectX (spit)). In which case, you would have re-invented the thin client again, without it being all that thin.
The difference in cost of a fully functional computer (with disk-like storage and all) and a thin client will never be high enough to justify their deployment. Desktop computers, Netbooks, and Phones will probably merge together, all with SSD based filesystems, input, and display devices, and a real, fully functional OS under the covers. Something like Chrome will end up being effectively a presentation or compatibility layer sitting on top of the OS, but the OS will be there, and will probably be Linux based for everybody other than Microsoft (and Apple if you draw a distinction between GNU/Mach and GNU/Linux).