Take WiFi. It is still assumed by many property-owners that they can, and should, control what is done with electromagnetic spectrum within their properties. Because WiFi is low-power, high-frequency waves that attenuate quickly, someone with a substantial footprint can make this dream come true.
Now they can do it with open source. Sputnik, which produces software which makes WiFi proprietary, which they call "venue-branded, access-controlled Wi-Fi networks," is now out with a version that supports the Netgear Open Source Wireless-G Router WRG614L.
This is one of the ironies of open source. Quick access to code lets you close things down just as quickly as you open things up. And it lets you get this to market inexpensively, in this case at prices starting at $99.
I should note here that Sputnik already supports a lot of closed-source routers, and its gear is aimed at building large networks or "hotzones." My problem is with the legal concept, the idea of property rights over unlicensed frequencies, which their gear enables.
The FCC has ruled this illegal, in the case of Logan Airport in Boston, and so long as this remains the case then competition from Sputnik-enabled networks is no problem for me.
But what East Coast Law can enable, West Coast Law can disable. And the price of electromagnetic freedom remains eternal vigilance. Just as with open source.