UI designers are making the same old fundamental "forgetting about the human being on the other side" mistakes—except this time their code looks better. Humans—not code validators—use interfaces.
I would disagree, because while designers are together they often talk shop about techniques and technologies, but one of the major benefits of standards-based design for the Web is that it encourages people to separate the design of material from its content, and thus make the content more accessible to a wider variety of people and devices. It's also easier to make attractive designs that work when you can separate elements of the page into modules that can be improved, rather than being stuck with systems that are so interdependent that it's impossible to fix things without starting, in essence, from scratch.
A simple example: when I rebuilt much of this website to use more Cascading Style Sheets (CSS) and less tables-based web design, I also re-did the colour scheme and some of the navigation. Some people didn't like the changes, and some of their comments were good ones. So I tweaked the design, and now it's better. Before I moved to CSS for some of my layout, those tweaks would have been much more difficult, and I wouldn't have done them, so this site would be harder to use (and less useful) today.
On the other hand, one hazard of CSS-based design is that is is easier for people to copy layouts wholesale without much effort—an issue Dave Shea (who did well at SXSW this year) covers today by saying:
Don't let the bastards bring you down. They can steal one of your works, but they can't steal your soul. Keep on creating because there's only one you, and the world is dimmer without your creative energy.
Perhaps the best parallel here is the fashion industry. Oddly enough, clothing designs (i.e. the cut and shape of a garment) cannot generally be copyrighted, while the design pattern of a fabric (i.e. flowers, stripes, etc.) sometimes can be.
So, the fashion industry is rife with knock-offs. But fashion designers continue to make money, and come up with new designs all the time. Even if someone rips off a designer's original CSS layout, that doesn't make the original designer less talented, and doesn't prevent him or her from coming up with better designs in the future. It also doesn't automatically make the site created with ripped-off CSS as good as or better than the original, because the original design was made for a specific purpose that the knock-off isn't.
Similarly, other companies can try to copy the iPod all they like (within the bounds of copyright and patent law and Apple's ferocious lawyers), but by the time they come out with a good-enough knock-off, Apple will have a new iPod Mini (or whatever) that is superior.
The balance of copyright law, and the idea of respect for creativity, is to reward the creator for new, innovative work. The few leeches who rip off designs wholesale might even help there, because they encourage the original designers not to rest on their laurels, and to come up with work that beats the pants off their older material that is getting copied.
I should add, however, that those who take a design outright without attribution or permission do open themselves up for legal challenges once the original designer finds out—which is damn likely—and so it still isn't a wise thing to do. Especially when many designers will be flattered and helpful if you simply ask to use a design in a non-commercial context, or offer a fair (often small) fee in a commercial one.