According to key Internet players, over 90% of bad request use DNS.
Cisco recently acquired OpenDNS probably for this main reason. Messing with DNS is not even on the radar for most end-users but OpenDNS actually makes it easy.
Problem: Your 11-year old has a brand-new Smartphone and you realise they have access to ANY content on the internet.
Solution: change to DNS from Google to OpenDNS
End result: no more phone confiscation arguments
This is a typical solution that should not be explained to non-technical or tech scared parents. Just get the most tech savvy adult in the family to configure it and forget about it, no nerd discussions or debates.
Downside: This is only a partial solution as most phones do not allow you to mess with the DNS settings for cellular.
So we can change stuff for WiFi only. Unfortunately, most of us are using cellular networks for internet access even when we are home.