Trunking comes in PVC and steel of various sizes. The plastic variety is most common due to lower costs, except in industrial environments where the extra protection against damage is needed (e.g. factory, garage, etc.).
Yes, cables clipped direct to the baseboard ("skirting board" in British parlance) or to walls are very common here, probably because so many of the walls in our buildings are solid masonry so chaneling out for cables can be a very labor-intensive and tiring job. That's where the surface trunking is very useful and makes a much neater job. The smallest size is about 5/8" square, the next about 1 x 5/8, so they're not too obtrusive (and can be painted over anyway).
[Edited for typos.]
[This message has been edited by pauluk (edited 04-26-2002).]
