I did the mistake of looking of it's algorithm after a few turns. After that it is not possible for the AI to exploit you any more. Or I haven't played long enough for the AI to discover it's algorithm has been exploited. So as an advice to other players, don't click on the button "see what the computer is thinking" until you feel you have deducted it's algorithm yourself. Takes away too much of the fun.
I read an article a while back that said good computer simulations should expect the human to usually not choose the same throw repeatedly, and especially not choose the throw if the player lost the previous time.
Also, humans tend to choose throws that make up an even distribution of R/P/S — that is, the chances of a rock being thrown after 2 paper and 2 scissors is much higher.
Doesn't seem too hard to beat it, since all you have to do is imagine what a person would most likely do given your history. Do scissors three times, and the AI will assume you'll do it again.