KDE4 introduced a stupid useless icon that you can't get rid of, in the upper right corner of the desktop. The developer of the relevant code has adamantly refused to introduce any possibility of making it optional; but a civic-minded third party created the "I Hate the Cashew!" "plasmoid" to make it go away. That's all well and good.
The bad news is that "I Hate the Cashew" is no longer maintained, and doesn't work anymore with the current version of KDE, 4.5.1 as I write this. The good news is that with some digging, I found a solution in a Web log comment from someone using the name "Newar," and that works. The trick: you can now move the cashew to your choice of corner. So move the panel out of the way temporarily (for instance to the left edge of the screen), move the cashew to a corner that will be covered by the panel (lower right), and then move the panel back to its usual location. The cashew is still theoretically there, but at least it's no longer all up in your face. Thank you, Newar!