graeme_p - 8:24 am on Jul 27, 2013 (gmt 0)
1) given the popularity of online #*$! (and the nuisance of false positives) it means a high proportion of households will opt out
2) this means that children from those households will be able to show their friends #*$!
3) that invalidates your strongest argument (that parents cannot control what others show their kids).