I had great difficulty getting in to the US (ORD) last week. I will grilled like never before. The reason was not terrorism but the officer thought I would outstay my welcome (not that I have ever done that on my 10 previous visits). He thought it was strange that I was travelling alone and that I had booked to stay in Chicago for one month for leisure purposes. I explained that I was renting an apartment and would use Chicago as a base and would visit a few other cities including Toronto. I literally pleaded with him showing my travel guides, diary and all sorts before he agreed to let me in.
I'm going to Toronto in a couple of days. Whilst I am not worried about being refused entry to Canada (I can live with that!), I'm worried that I might not get back in to the US to finish my holiday here!