The key to mining information from any database is consistency in entries. Any column in a database can be searchable - the value of the search lies in making "free form" entries look the same. Huh???
In QuickBooks, many fields are defined - name, address, account. Fields such as Memo are "free form", meaning you can write whatever you want. If you will need to search that field for information, then you will need to decide on a format for the Memo field.
For example, my real estate clients collect earnest money from their buyer clients. Rather that create an invoice and then receive payment, I just use the Make Deposit from Banking to enter these checks. A client may buy multiple properties over a period of time so to identify the property I enter the address in the memo field. By using the same format every time, I can perform a search function of the memo field and find every transaction related to a particular property. This is especially helpful in reconciling the liability account to ensure that the liability was relieved after closing. It is also an easy way to verify that an earnest deposit was made and when.