I'm glad I found this thread. It's something that concerns me too. I tend to wipe my Canada phone and have everything in the cloud when coming from the U.S. My work phone is clean, but I'd still feel unhappy with strangers rooting around my business. My computer does have some porn on it, but thankfully I've never been asked to allow them to root around its files. Do we have to give them access to our computers when they ask?
I'm not about to tell them I'm there for hanky panky so I've always said tourism. I like the city, which is true, and I like how far my money goes.
If I said I was coming to visit a friend without a real person in mind, would that be dangerous? Would they go down that path of asking for a name, then history, and look for holes in my story? I could easily think of a friend and use all that information.
I could also say I'm thinking of buying real estate, which is also true, but would that arouse class resentments?
On another message board, I read a report of an aggressive border agent coming across text conversations with agencies and turning that person away. That would be horrible -- presumably you could never enter the country again.