This might be unneighborly, since it'd mean that your nosy neighbors can't piggyback off your wireless connection anymore.
But for the price of a can of house paint, this may very well be one of the most cost-effective ways to secure your office wireless network against hackers and freeloaders, particularly in a time of thrift.
Researchers at the University of Tokyo have blended paint with aluminium iron oxide, which has been found to resonate at the same frequencies used by Wi-Fi, thus canceling out any electromagnetic waves in that frequency. It sounds like really cool Minority Report stuff.
Of course, it's only bound to attract the attention of every hacker out there who can't resist a challenge. And it reduces your chances of receiving love notes like this.