Modding has never been main stream, but the idea of having a custom computer may be wearing into the mass markets if ECS has anything say about it.  Elitegroup Computer Systems (ECS) is primarily a motherboard company, but has a Simply Smart philosophy and has won over 150 awards for it's design.  ECS had a display at Coputex 2009, and had a rather interesting prototype for showing off their Small-Form-Factor Desktop System, some might even call it a mod, but I would call it the compu-vase.  Yes that's right.  ECS built a mod out of a porcelain vase to showcase their latest system. The compu-vase looks real, because it is real porcelain.

The mod ... er ... prototype is also packed with features.  An Intel Atom CPU, 1GB RAM, Blu-Ray, NVIDIA ION Graphics, and HDMI Output.  While ECS isn't a computer manufacturer, it could lure some companies into expanding their model designs.  I can definitely see more and more motherboard/component manufacturers doing some kind of mod for their next booth.

More info at gizmag.com