I’m no design guru (although I’ve been learning a little about validating code), but I’ve often stolen designs and design ideas from other people. For important front ends, yes, I try to make it unique. But a lot of times when starting a blog or making a basic template, you need to rely on other people’s templates (or hopefully your own). That is how you learn.
Nowadays the fun stuff is DHTML, and backend scripting, so merely stealing code and graphics doesn’t help much anyway.
A brilliant designer got all riled when I suggested she chill out about other people taking her code. Hey, HTML is supposed to be transparent. It was a conscious decision by w3 and developers for browsers.
That said, when I’ve taken other people’s style sheets or even HTML, sometimes I can get hopelessly lost in their code. So when I need to tweak something or correct some bug, I am truely clueless.
I like platforms like wordpress or blogger which gave you lots of templates and skins to choose from. Some people I know have a great visual sense and others do not. At this point, the web development process is specialized enough that design tasks can be delegated and delayed while the backend crap is taken care of.