The basic benefit to storing information about guests is that it can help you to provide those guests with a better experience, thus making them more likely to keep returning to your hotel. The major risk is that guests will be offended or, if your storage is compromised, angered by the loss of their personal data.
It is important for hotels to make business customers feel welcome and important. Therefore, storing information about them can be helpful. If the staff has access to good information about a guest, they can be sure to have the things that guest likes available when they come to a hotel. This will make the guest feel important and special and will make them more likely to keep coming to that hotel.
The problem is that not everyone likes to have information like this stored. They may feel that it is an invasion of privacy. If your computers that have the data on them happen to get hacked or otherwise compromised, you would have a large number of very angry customers.
Thus, storing information about guests is generally a good idea, but does carry some risks.