http://www.epitiro.com/
" "Our data shows that connectivity over Wi-Fi degrades broadband performance considerably in typical circumstances," JP Curley, CTO of Epitiro, said in the report. "Consumers who are experiencing performance issues with Wi-Fi should take steps to improve their home environment or connect directly via wired Ethernet."
Epitiro's research -- based on reports from 14,001 users in the UK, USA, Italy and Spain -- states consumers lose an average of 30 percent of download speed and face an increase in latency of 10-20 percent when using Wi-Fi connections in the home. Such applications as on-line gaming, VoIP telephony and video streaming are potentially impacted using Wi-Fi and
downloading large files such as MP3s, videos and programs will take longer."
Ok, they say nothing about encryption. But everything about interference