This story is being sensationalized quite a bit.
First, lets clarify what router is being used for the public hotspot service - Comcast is doing this primarly with the Arris TG862 which is a Cable Modem/Telephony Gateway/Wireless-N router all in one, and to be specific, they are only doing it to units that are leased from Comcast as they legally cannot make modifications to your equipment without consent.
Second, Comcast has set up these units so that they will be using not only a separate wifi channel than what you have your wlan configured for, it will also be using separate docsis channels so that it will have minimal, if any impact on subscriber services.
Finally, Comcast has confirmed that subscribers can opt-out at any time by contacting support.
It should be noted that if you have your own router and want it attached to the TG862 or similar equipment, you should have already contaced Comcast to have support place the gateway into bridge mode and disable the wifi to eliminate interferance and configuration issues.
Not saying that I agree with what Comcast is doing, but people are making a much bigger deal out of this than what it really is. If you don't already have your own router, go buy one and have Comcast put your gateway into bridge mode and call it a day. You will probably find that the wifi on a dedicated router works much better anyway and likely to have fewer potential security holes.