Tweeting on hosted trips: when does it become shilling?

I’ve just got back from what was quite possibly the most fantastic holiday of my life. After picking up a car in Las Vegas airport, my wife and I drove through Utah, then Grand Teton and Yellowstone National Parks into Montana, before finishing with a few days in Seattle and Vancouver. I’m not generally prone to hyperbole, but I didn’t exactly hold back with my enthusiasm for the journey on Twitter.