I signed up for a Diamond Trial for the sole purpose of using the benefits for a single stay at the Park Hyatt Tokyo, and possibly to use up the suite upgrades over the next year. But the service I received impressed me so much that I forcibly completed the challenge to stay a Diamond into 2014.
The generous benefits of the trial lured me in, and they ended up getting a lot of extra business as a result. If a hotel has confidence in the service they provide, then offering such sweeteners may not be such a bad idea.