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This paper studies the effectiveness of this approach towards online copyright enforcement, using both a consumer survey and a newly developed non-infringing technology for BitTorrent monitoring. While a small group of respondents download less from illegal sources or claim to have stopped doing so, no impact is found on the percentage of the Dutch population downloading from illegal sources.
The torrent monitoring technique also shows that if you are downloading a public torrent, anyone can find out.
Technically it doesn't make sense but from a functionaly point of view (the user experience) it makes much sense.
If you do something right once, someone will ask you to do it again.