Now, I don't know the truth, but even assuming he had documents they wanted to get their hands on, or files on his devices that they thought pertinent they could have handled the whole thing in 30 minutes max and then let him go on his merry way.
That they held him - almost to the minute - for the legal maximum of 9 hours looks not only vindictive it looks as if they indeed intended to send a message.
Put that into context with other documented occurrences, like the totally senseless destruction of hardware and sandbagging the Guardian into this action (and yes, The Guardian has here more credibility then the UK government, which denies any threats, but that's just me) and we get a whole other picture.
While totalitarian police state may be an over exaggeration , we should be very careful about the direction this is going into.
Assume you're a journalist and suddenly the government(s) have a truckload embarrassing material on you (from Google searches, Facebook accounts, Skype calls and whatever your friendly operating system leaks directly to the NSA's vacuum cleaners) to directly blackmail you.
And no, I don't consider myself a member of the black helicopter faction, but nevertheless find those developments extremely worrying.