What do people usually put into the "reference" field of a partner? I'm looking for examples.
The purpose of this field is to ease search.
If you are on the customers list view and start typing something in the search bar, it will in fact search on several fields of the Customers object and the reference is one of them (along with "Name" and "email address"). It is the same principle for other objects like "Products" or "Users" (where it does the same with the field "login"). So what you would typically enter there is a customer code that identifies uniquely (or not, it's up to you) each customer.
In fact, in v6, it even goes one step further because if the search result finds at least 1 record, it will display the result based on the "reference" field only and not on the "name" field. However this latest mechanism has not been kept in v7; I suspect because the difference in speed wouldn't be affected anyway.
You can put anything you want in that field because it's absolutely useless. You will never see it again.
In any company, try to contact them and have them search by your name. They will always ask you for an account number. In v7 they removed the account number reference and search so when you want to find a customer, you get to look for their name. Hopefully you only have 10 customers and this won't be a problem. If you have more, have fun.
More useless "improvements."
It's clearly 'old school' to assign a code or a reference to contacts. Nowadays, people do not work with references anymore, they just use the plain name.
In a lot of software, the users must use a code to reference a contact from another document (sale order, ...) We just keep this field because when you migrate from another software to OpenERP, the users can keep using their usual references. It also helps for the migration to have a copy in OpenERP of the reference field from the other software.
It can also help searching quickly the most used contacts. As you can write the reference to quickly find a contact.
This is just false. Any and every time you call any company of any size, what is the first thing they ask you for? Your account number. Since v7 removed this feature, this is a backtrack of sensible and functional performance in your system. Do you think companies like T-Mobile are going to search for a customer "John Smith" by typing in that common name? Absolutely not. Any company of any size would look at what you've done and shudder thinking about searching by names. The customer search feature is useless in v7.