Take the much misused button. On the web its really for submitting data. At Sprint we even made standards to this effect some time back. We had to because it was so often misused as a "more important" link. Its big and (at the time) red, so it must be more important than a simple colored, underlined word. The current Sprint home page has a button for "all phones" that does nothing more than the links above it, except be big and yellow. Other prominent examples abound.
I've always given particular grief to interactive systems due to their immaturity about such issues. Newspapers don't mess up this sort of thing. Road signs, regardless of country, are often another good one. In the US orange, for example, means construction.
And nothing else. Reserving it for construction means that any driver can pay special attention to such signs and know there is an exception message contained therein. If you've never been here, there's a temporary, probably dangerous situation. If you are used to this place, disregard all you know and start looking at the signs again because something probably changed (like, the road is closed). This is all well reinforced by using the same orange for pylons, with white stripes for barricades, etc. I even saw a team of guys paving on the way to work this morning, everyone one of them wearing construction-orange T-shirts.
Which makes this annoying:
This is near my house, but I saw scads of them throughout extreme northern California. Something the highway department thinks is just "really important" at the time gets a sign. Often, its just not that important. Like, 6% grade ahead. Which is perfectly well served with a yellow sign everywhere else in the world. Yellow is a fine color for warning signs.
What I think of this is pretty much what I think of over-using buttons. If there is a problem that legitimately is solved by using an orange sign, you need to solve it some other way instead. Aside from misleading everyone, eventually the value of the orange sign will be diluted, and comprehension or urgency failures will occur. In traffic signage, this could have much more dire consequences than any website.