[silverlake]

Toxicological findings in cases of alleged drug-facilitated sexual assault in the United Kingdom over a 3-year period: http://www.ncbi.nlm.nih.gov/pubmed/16054005

TL;DR: 1014 people claimed they were drugged and sexually assaulted. "In 21 cases (2%), a sedative or disinhibiting drug was detected..." So-called "date rape" drugs were a subset of these cases.

[jamieb]

From your source: "Illicit drugs were detected in 344 cases (34%)"

[Nursie]

Illicit does not mean unwitting or unwillingly taken.

(Again, no judgement on those that choose to use drugs, I certainly do and I think that drug users are as deserving of protection as anyone else)