Well, if we're being paranoid they probably don't need to touch your personal belongings. They just have to have a look at the bed sheets after you've slept on them.

...or to get your DNA they can work it out from the "deposited" DNA of your close relatives. There will be no hiding! :P

Sure! What I specifically meant (sorry, was unclear) is, how long before such activity becomes lucrative enough for hotels to routinely perform? ("hotels" == entities in a completely unrelated lines of business) I.e., there is stable market for these data and the procedure isn't very costly in recurring expenses (no costly extraction from "noisy" support).

Would that be legal by today's laws?