It basically means you can explicitly request that someone not credit you in a derivative work, even though the license ordinarily requires it. I'm not really sure why you'd use it either - maybe if someone created a derivative of your work that you hated so much that you didn't want anyone knowing it was based on something you did.
Warning: I'm going to rant a little bit here
Is this something that the Arduino project really needs? I mean can you really force someone to not give attribution? And does this retro-actively modify the share-alike clause of CC? That is, if someone makes a derivative of evil-arduino do they have not give credit? or do they have to credit both or what?
If you ask me (which you didnt 
) this license-hacking seems like its unnecessary and, well, somewhat creepy. I mean, who cares if someone makes a shitty derivative?
Why do I feel strongly this? Well because I've seen what can happen when people try to destroy derivatives: Historically, some people on the NetBSD team hate(d) OpenBSD and the OpenBSD project leader and they would have loved to say "you can't call your project a BSD because we dont like your project, or you!" But (luckily) they couldn't.
Nobody really confuses the two projects, and some people still don't like OpenBSD but you can't really deny that is a BSD derivative, and a very good one that is quite popular with some. The flame war bogged down both groups and was a waste of f'ing time.
(I'm somewhat simplifying the long and tedious netbsd/openbsd flame war here but i think that's probably for the best 
)
I urge you to reconsider this clause, I see no positive outcomes and only bad ones. However, I will relent if you have a really good example of when this is essential to the survival of the Arduino project.
limor