Have you cleaned your whiteboard today?
A contractor I worked with told me about a previous gig where the office had been redecorated so that every wall was covered, floor to ceiling, in whiteboard material. By contrast, I visted a workplace last year with a floor full of techies and no whiteboards. In one of those places the management understood how developers work and wanted to encourage communication, and the other place it didn't.
People have also joshed me for the way my occasional bouts of scrupulously cleaning whiteboards. But whiteboards should be clean. They are monuments to the ad hoc. A blank whiteboard is an invitation to share ideas or workthrough problems. A whiteboard covered in stuff is a deterrent to use. Plus, after a while, the ink stains the whiteboard; it takes a lot of elbow grease, and perhaps chemicals, to restore a grubby whiteboard to pristine blankness.
The worst thing you can write on a whiteboard is "please leave".
It's all about the appopriate use of technology. Whiteboards are not the right place to leave keep important information. Rough out some pseudo-code on a whiteboard but for heaven's sake transfer the result into some UML tool. Put the new plan into MS Project as soon as the whiteboard session is finished.
Above all, don't use a whiteboard for static data like the team's phone numbers. Stick a page on the wiki. And as for pretending it is a wall planner...Use a spreadsheet. Use Google Calendar. Just keep the whitebords free for ephemera.
I'm afraid this also applies to the darling doodles left after the last "Take your kids to work" day.
So, before your place of work this evening, have a look around: is there a whiteboard which needs cleaning?