Olympics tickets are only available via official box offices or the website for the London Olympics and Paralympic Games, with non-legit sales pursued for punishment in the form of fines up to £20,000. According to a recent article about these heightened security measures, President of The Society of the Golden Keys (a professional concierge association) Ron Crowdy was quoted as saying "concierges will come under 'huge pressure' to obtain Olympic tickets for guests…'[S]ome of our most trusted agents seem to be under the impression that they can sell tickets legally.'"
Meanwhile, reps from The Cavendish and The Waldorf Hilton are educating staff members about the illegality about such sales. Future London visitors, do your concierge a favor and don't try to gently nudge them into finding games tickets for you. Unless you've got a £20,000 note to slip 'em rather than a £20, chances are the whining won't do much other than annoy the law abiding employees.