Wednesday 22 February 2012 9.26am
Actually many BT users' provide a semi- open service already. Newer HomeHubs provide a second Fon
wifi channel. This is a reciprocal network - if you have Fon you can connect to any other Fon. BT cheekily also provides a paid OpenReach service from the newest HomeHubs.
There are potential security implications behind leaving your main network "open". With a bit if technical knowledge and settings these can be overcome, but just removing wifi security is not recommended.
The safest way is to set a second network (from the same router/broadband but it will act like a second network). You could either use something like Fon mentioned above, or if you use an open source firmware like DD-Wrt or Tomato it's baked in.
In summary if you don't understand it, don't do it.