I followed a group of guests around. They went into my vivarium building with 8 exhibits, went out briefly to use the toilets, back into the building, out to get a drink, back into the building, out to get something to eat, back into the building... I watched them go in and out 8 times before I had to stop watching them.
One guest said she had run out of money (although she still had $800 in her pocket and there were lots of free ATMs around), so she could not afford a drink to quench her thirst. She ran from one shop to the next, only to realize that she had no money to buy anything and head to the next shop. Endlessly round and round all the shops in the same food court. Finally she decided to go home.
There is definitly room for improvement in the guest AI!
Watching the guests can be quite entertaining.